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The structure of part of a DNA double helix

Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. The main role of DNA is the long-term storage of information and it is often compared to a set of blueprints, since DNA contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information. Image File history File links Download high resolution version (799x2000, 915 KB) Summary An overview of the structure of DNA. Created by Michael Ströck (mstroeck) on February 8, 2006. ... Image File history File links Download high resolution version (799x2000, 915 KB) Summary An overview of the structure of DNA. Created by Michael Ströck (mstroeck) on February 8, 2006. ... Look up nucleic acid in Wiktionary, the free dictionary. ... DNA, the molecular basis for inheritance. ... Views of a Foetus in the Womb, Leonardo da Vinci, ca. ... For other uses, see Life (disambiguation). ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell. Cells in culture, stained for keratin (red) and DNA (green). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions... In science, a molecule is a group of atoms in a definite arrangement held together by chemical bonds. ... For a non-technical introduction to the topic, see Introduction to Genetics. ...


Chemically, DNA is a long polymer of simple units called nucleotides, with a backbone made of sugars and phosphate atoms joined by ester bonds. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription. Most of these RNA molecules are used to synthesize proteins, but others are used directly in structures such as ribosomes and spliceosomes. A polymer is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... A carboxylic acid ester. ... Adenine Guanine Thymine Cytosine ... A series of codons in part of a mRNA molecule. ... Phenylalanine is one of the standard amino acids. ... Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... A spliceosome is a complex of RNA and many protein subunits called snRNPs, that removes the non-coding introns from unprocessed mRNA. Spliceosomes are unique to eukaryotic mRNA as the mRNA of prokaryotes lack introns. ...


Within cells, DNA is organized into structures called chromosomes and the set of chromosomes within a cell make up a genome. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms such as animals, plants, and fungi store their DNA inside the cell nucleus, while in prokaryotes such as bacteria it is found in the cell's cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA, which helps control its interactions with other proteins and thereby control which genes are transcribed. Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... This does not adequately cite its references or sources. ... It has been suggested that DNA replicate, Replisome, Replication fork, Lagging strand, Leading strand be merged into this article or section. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Protista Alternative phylogeny Unikonta Opisthokonta Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... For other uses, see Animal (disambiguation). ... Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta—liverworts Anthocerotophyta—hornworts Bryophyta—mosses Vascular plants (tracheophytes) †Rhyniophyta—rhyniophytes †Zosterophyllophyta—zosterophylls Lycopodiophyta—clubmosses †Trimerophytophyta—trimerophytes Pteridophyta—ferns and horsetails Seed plants (spermatophytes) †Pteridospermatophyta—seed ferns Pinophyta—conifers Cycadophyta—cycads Ginkgophyta—ginkgo Gnetophyta—gnetae Magnoliophyta—flowering plants... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... Prokaryotes (pro-KAR-ee-oht) (from Old Greek pro- before + karyon nut or kernel, referring to the cell nucleus, + suffix -otos, pl. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... It has been suggested that Cytoplast be merged into this article or section. ... Chromatin is the complex of DNA and protein found inside the nuclei of eukaryotic cells. ... Schematic representation of the assembly of the core histones into the nucleosome. ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ...

Contents

Physical and chemical properties

The chemical structure of DNA.
The chemical structure of DNA.

DNA is a long polymer made from repeating units called nucleotides.[1][2] The DNA chain is 22 to 24 Ångströms wide (2.2 to 2.4 nanometres), and one nucleotide unit is 3.3 Ångstroms (0.33 nanometres) long.[3] Although each individual repeating unit is very small, DNA polymers can be enormous molecules containing millions of nucleotides. For instance, the largest human chromosome, chromosome number 1, is 220 million base pairs long.[4] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A polymer is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... An Ã¥ngström or aangstroem (the official transliteration), or angstrom (symbol Ã…) is a non-SI unit of length that is internationally recognized, equal to 0. ... A nanometre (American spelling: nanometer, symbol nm) is a unit of length in the metric system, equal to one thousand-millionth of a metre, which is the current SI base unit of length. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Base pairs, of a DNA molecule. ...


In living organisms, DNA does not usually exist as a single molecule, but instead as a tightly-associated pair of molecules.[5][6] These two long strands entwine like vines, in the shape of a double helix. The nucleotide repeats contain both the segment of the backbone of the molecule, which holds the chain together, and a base, which interacts with the other DNA strand in the helix. In general, a base linked to a sugar is called a nucleoside and a base linked to a sugar and one or more phosphate groups is called a nucleotide. If multiple nucleotides are linked together, as in DNA, this polymer is referred to as a polynucleotide.[7] A helix (pl: helices), from the Greek word έλικας/έλιξ, is a twisted shape like a spring, screw or a spiral (correctly termed helical) staircase. ... Nucleosides are glycosylamines made by attaching a nucleobase (often reffered to simply as bases) to a ribose ring. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... Polynucleotide literally means many nucleotides. ...


The backbone of the DNA strand is made from alternating phosphate and sugar residues.[8] The sugar in DNA is 2-deoxyribose, which is a pentose (five carbon) sugar. The sugars are joined together by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings. These asymmetric bonds mean a strand of DNA has a direction. In a double helix the direction of the nucleotides in one strand is opposite to their direction in the other strand. This arrangement of DNA strands is called antiparallel. The asymmetric ends of DNA strands are referred to as the 5′ (five prime) and 3′ (three prime) ends. One of the major differences between DNA and RNA is the sugar, with 2-deoxyribose being replaced by the alternative pentose sugar ribose in RNA.[6] Above is a ball-and-stick model of the inorganic hydrogenphosphate anion (HPO42−). Colour coding: P (orange); O (red); H (white). ... Lactose is a disaccharide found in milk. ... A pentose is a monosaccharide with five carbon atoms. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Standard atomic weight 12. ... Diagram of phosphodiester bonds between nucleotides A phosphodiester bond is a group of strong covalent bonds between the phosphorus atom in a phosphate group and two other molecules over two ester bonds. ... Properties In chemistry and physics, an atom (Greek ἄτομος or átomos meaning indivisible) is the smallest particle still characterizing a chemical element. ... Covalent bonding is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or sometimes between atoms and other covalent bonds. ... A diagram of a furanose (sugar-ring) molecule with carbons labelled numerically Directionality, in molecular biology, refers to the end-to-end chemical orientation of a single strand of nucleic acid. ... A diagram of a furanose (sugar-ring) molecule with carbons labelled numerically Directionality, in molecular biology, refers to the end-to-end chemical orientation of a single strand of nucleic acid. ... Ribose Ribose, primarily seen as D-ribose, is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. ...


The DNA double helix is stabilized by hydrogen bonds between the bases attached to the two strands. The four bases found in DNA are adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T). These four bases are shown below and are attached to the sugar/phosphate to form the complete nucleotide, as shown for adenosine monophosphate. An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... This article or section does not adequately cite its references or sources. ... Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at... Guanine is one of the five main nucleobases found in the nucleic acids DNA and RNA; the others being adenine, cytosine, thymine, and uracil. ... For the similarly-spelled vitamin compound, see Thiamine Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ...


These bases are classified into two types; adenine and guanine are fused five- and six-membered heterocyclic compounds called purines, while cytosine and thymine are six-membered rings called pyrimidines.[7] A fifth pyrimidine base, called uracil (U), usually takes the place of thymine in RNA and differs from thymine by lacking a methyl group on its ring. Uracil is not usually found in DNA, occurring only as a breakdown product of cytosine, but a very rare exception to this rule is a bacterial virus called PBS1 that contains uracil in its DNA.[9] In contrast, following synthesis of certain RNA molecules, a significant number of the uracils are converted to thymines by the enzymatic addition of the missing methyl group. This occurs mostly on structural and enzymatic RNAs like transfer RNAs and ribosomal RNA.[10] Pyridine a simple heterocyclic compound Heterocyclic compounds are organic compounds which contain a ring structure containing atoms in addition to carbon, such as sulfur, oxygen or nitrogen, as part of the ring. ... Purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. ... Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring [1]. It is isomeric with two other forms of diazine. ... Uracil is a pyrimidine which is common and naturally occurring. ... In chemistry a methyl-group is a hydrophobic Alkyl functional group which is derived from methane (CH4). ... This article or section does not cite its references or sources. ... It has been suggested that Queuine be merged into this article or section. ... Ribosomal RNA (rRNA), a type of RNA synthesized in the nucleolus by RNA Pol I, is the central component of the ribosome, the protein manufacturing machinery of all living cells. ...

Animation of the structure of a section of DNA. The bases lie horizontally between the two spiraling strands. Large version
Animation of the structure of a section of DNA. The bases lie horizontally between the two spiraling strands. Large version[11]

The double helix is a right-handed spiral. As the DNA strands wind around each other, they leave gaps between each set of phosphate backbones, revealing the sides of the bases inside (see animation). There are two of these grooves twisting around the surface of the double helix: one groove, the major groove, is 22 Å wide and the other, the minor groove, is 12 Å wide.[12] The narrowness of the minor groove means that the edges of the bases are more accessible in the major groove. As a result, proteins like transcription factors that can bind to specific sequences in double-stranded DNA usually make contacts to the sides of the bases exposed in the major groove.[13] Image File history File links DNA_orbit_animated_small. ... Image File history File links No higher resolution available. ... In molecular biology, a transcription factor is a protein that binds DNA at a specific promoter or enhancer region or site, where it regulates transcription. ...


Base pairing

Further information: Base pair
At top, a GC base pair with three hydrogen bonds. At the bottom, AT base pair with two hydrogen bonds. Hydrogen bonds are shown as dashed lines.

Each type of base on one strand forms a bond with just one type of base on the other strand. This is called complementary base pairing. Here, purines form hydrogen bonds to pyrimidines, with A bonding only to T, and C bonding only to G. This arrangement of two nucleotides binding together across the double helix is called a base pair. In a double helix, the two strands are also held together via forces generated by the hydrophobic effect and pi stacking, which are not influenced by the sequence of the DNA.[14] As hydrogen bonds are not covalent, they can be broken and rejoined relatively easily. The two strands of DNA in a double helix can therefore be pulled apart like a zipper, either by a mechanical force or high temperature.[15] As a result of this complementarity, all the information in the double-stranded sequence of a DNA helix is duplicated on each strand, which is vital in DNA replication. Indeed, this reversible and specific interaction between complementary base pairs is critical for all the functions of DNA in living organisms.[1] Base pairs, of a DNA molecule. ... Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... Base pairs, of a DNA molecule. ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... In physics, force is an influence that may cause an object to accelerate. ... The hydrophobic effect is the property that nonpolar molecules like to self-associate in the presence of aqueous solution. ... It has been suggested that this article or section be merged into Stacking (chemistry). ... Covalent bonding is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or sometimes between atoms and other covalent bonds. ... This article includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ...


The two types of base pairs form different numbers of hydrogen bonds, AT forming two hydrogen bonds, and GC forming three hydrogen bonds (see figures, left). The GC base pair is therefore stronger than the AT base pair. As a result, it is both the percentage of GC base pairs and the overall length of a DNA double helix that determine the strength of the association between the two strands of DNA. Long DNA helices with a high GC content have stronger-interacting strands, while short helices with high AT content have weaker-interacting strands.[16] Parts of the DNA double helix that need to separate easily, such as the TATAAT Pribnow box in bacterial promoters, tend to have sequences with a high AT content, making the strands easier to pull apart.[17] In the laboratory, the strength of this interaction can be measured by finding the temperature required to break the hydrogen bonds, their melting temperature (also called Tm value). When all the base pairs in a DNA double helix melt, the strands separate and exist in solution as two entirely independent molecules. These single-stranded DNA molecules have no single common shape, but some conformations are more stable than others.[18] The Pribnow box (also known as the Pribnow-Schaller box) is the sequence TATAAT of six nucleotides (thymine-adenine-thymine-etc. ... A promoter is a DNA sequence that contains the information, in the form of DNA sequences, that permits the proper activation or repression of the gene which it controls, i. ... The dissociation of a double-stranded DNA molecule is often referred to as melting because it occurs quickly once a certain temperature has been reached. ...


Sense and antisense

Further information: Sense (molecular biology)

A DNA sequence is called "sense" if its sequence is the same as that of a messenger RNA copy that is translated into protein. The sequence on the opposite strand is complementary to the sense sequence and is therefore called the "antisense" sequence. Since RNA polymerases work by making a complementary copy of their templates, it is this antisense strand that is the template for producing the sense messenger RNA. Both sense and antisense sequences can exist on different parts of the same strand of DNA (i.e. both strands contain both sense and antisense sequences). In both prokaryotes and eukaryotes, antisense RNA sequences are produced, but the functions of these RNAs are not entirely clear.[19] One proposal is that antisense RNAs are involved in regulating gene expression through RNA-RNA base pairing.[20] Sense, when applied in a molecular biology context, is a general concept used to compare the polarity of nucleic acid molecules, particularly RNA, to other nucleic acid molecules. ... The life cycle of an mRNA in a eukaryotic cell. ... This article does not cite any references or sources. ... Gene expression, or simply expression, is the process by which a genes DNA sequence is converted into functional proteins. ...


A few DNA sequences in prokaryotes and eukaryotes, and more in plasmids and viruses, blur the distinction made above between sense and antisense strands by having overlapping genes.[21] In these cases, some DNA sequences do double duty, encoding one protein when read 5′ to 3′ along one strand, and a second protein when read in the opposite direction (still 5′ to 3′) along the other strand. In bacteria, this overlap may be involved in the regulation of gene transcription,[22] while in viruses, overlapping genes increase the amount of information that can be encoded within the small viral genome.[23] Another way of reducing genome size is seen in some viruses that contain linear or circular single-stranded DNA as their genetic material.[24][25] Figure 1: Schematic drawing of a bacterium with plasmids enclosed. ... Groups I: dsDNA viruses II: ssDNA viruses III: dsRNA viruses IV: (+)ssRNA viruses V: (-)ssRNA viruses VI: ssRNA-RT viruses VII: dsDNA-RT viruses A virus (from the Latin noun virus, meaning toxin or poison) is a microscopic particle (ranging in size from 20 - 300 nm) that can infect the... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ...


Supercoiling

Further information: DNA supercoil

DNA can be twisted like a rope in a process called DNA supercoiling. With DNA in its "relaxed" state, a strand usually circles the axis of the double helix once every 10.4 base pairs, but if the DNA is twisted the strands become more tightly or more loosely wound.[26] If the DNA is twisted in the direction of the helix, this is positive supercoiling, and the bases are held more tightly together. If they are twisted in the opposite direction, this is negative supercoiling, and the bases come apart more easily. In nature, most DNA has slight negative supercoiling that is introduced by enzymes called topoisomerases.[27] These enzymes are also needed to relieve the twisting stresses introduced into DNA strands during processes such as transcription and DNA replication.[28] In a relaxed double-helical segment of DNA, the two strands twist around the helical axis once every 10. ... In a relaxed double-helical segment of DNA, the two strands twist around the helical axis once every 10. ... Topoisomerase I solves the problem caused by tension generated by winding/unwinding of DNA. It wraps around DNA and makes a cut permitting the helix to spin. ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... It has been suggested that DNA replicate, Replisome, Replication fork, Lagging strand, Leading strand be merged into this article or section. ...

From left to right, the structures of A, B and Z DNA

Image File history File links Download high-resolution version (2486x1620, 2113 KB) By Richard Wheeler (Zephyris) 2007. ... Image File history File links Download high-resolution version (2486x1620, 2113 KB) By Richard Wheeler (Zephyris) 2007. ...

Alternative double-helical structures

Further information: Mechanical properties of DNA

DNA exists in several possible conformations. The conformations so far identified are: A-DNA, B-DNA, C-DNA, D-DNA,[29] E-DNA,[30] H-DNA,[31] L-DNA,[29] P-DNA,[32] and Z-DNA.[8][33] However, only A-DNA, B-DNA, and Z-DNA have been observed in naturally occurring biological systems. Which conformation DNA adopts depends on the sequence of the DNA, the amount and direction of supercoiling, chemical modifications of the bases and also solution conditions, such as the concentration of metal ions and polyamines.[34] Of these three conformations, the "B" form described above is most common under the conditions found in cells.[35] The two alternative double-helical forms of DNA differ in their geometry and dimensions. The mechanical properties of DNA are closly related to its molecular structure and the relative weakness of the hydrogen bonds and electronic interactions that hold strands of DNA together compared to the strength of the bonds within each strand. ... Conformational isomerism is the phenomenon of molecules with the same structural formula but different conformations (conformers) of atoms about a rotating bond. ... The A-DNA structure. ... The Z-DNA structure. ... Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily loses electrons to form positive ions (cations) and has metallic bonds between metal atoms. ... An electrostatic potential map of the nitrate ion (NO3−). Areas coloured red are lower in energy than areas colored yellow An ion is an atom or group of atoms which have lost or gained one or more electrons, making them negatively or positively charged. ... The polyamines are organic compounds having two or more primary amino groups - such as putrescine, cadaverine, spermidine, and spermine - that are growth factors in both eucaryotic and procaryotic cells. ...


The A form is a wider right-handed spiral, with a shallow and wide minor groove and a narrower and deeper major groove. The A form occurs under non-physiological conditions in dehydrated samples of DNA, while in the cell it may be produced in hybrid pairings of DNA and RNA strands, as well as in enzyme-DNA complexes.[36][37] Segments of DNA where the bases have been chemically-modified by methylation may undergo a larger change in conformation and adopt the Z form. Here, the strands turn about the helical axis in a left-handed spiral, the opposite of the more common B form.[38] These unusual structures can be recognised by specific Z-DNA binding proteins and may be involved in the regulation of transcription.[39] Methylation is a term used in the chemical sciences to denote the attachment or substitution of a methyl group on various substrates. ... The Z-DNA structure. ...

Structure of a DNA quadruplex formed by telomere repeats. The conformation of the DNA backbone diverges significantly from the typical helical structure
Structure of a DNA quadruplex formed by telomere repeats. The conformation of the DNA backbone diverges significantly from the typical helical structure[40]

Image File history File links Size of this preview: 658 × 600 pixelsFull resolution (1316 × 1200 pixel, file size: 1. ... Image File history File links Size of this preview: 658 × 600 pixelsFull resolution (1316 × 1200 pixel, file size: 1. ... A telomere is a region of highly repetitive DNA at the end of a chromosome that functions as a disposable buffer. ...

Quadruplex structures

At the ends of the linear chromosomes are specialized regions of DNA called telomeres. The main function of these regions is to allow the cell to replicate chromosome ends using the enzyme telomerase, as the enzymes that normally replicate DNA cannot copy the extreme 3′ ends of chromosomes.[41] As a result, if a chromosome lacked telomeres it would become shorter each time it was replicated. These specialized chromosome caps also help protect the DNA ends from exonucleases and stop the DNA repair systems in the cell from treating them as damage to be corrected.[42] In human cells, telomeres are usually lengths of single-stranded DNA containing several thousand repeats of a simple TTAGGG sequence.[43] Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... A telomere is a region of highly repetitive DNA at the end of a chromosome that functions as a disposable buffer. ... Telomerase is an enzyme that adds specific DNA sequence repeats (TTAGGG in all vertebrates) to the 3 (three prime) end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosomes. ... Exonucleases are enzymes that cleave nucleotides one at a time from an end of a polynucleotide chain. ... DNA damage resulting in multiple broken chromosomes DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. ...


These guanine-rich sequences may stabilize chromosome ends by forming very unusual structures of stacked sets of four-base units, rather than the usual base pairs found in other DNA molecules. Here, four guanine bases form a flat plate and these flat four-base units then stack on top of each other, to form a stable G-quadruplex structure.[44] These structures are stabilized by hydrogen bonding between the edges of the bases and chelation of a metal ion in the centre of each four-base unit. The structure shown to the left is a top view of the quadruplex formed by a DNA sequence found in human telomere repeats. The single DNA strand forms a loop, with the sets of four bases stacking in a central quadruplex three plates deep. In the space at the centre of the stacked bases are three chelated potassium ions.[45] Other structures can also be formed, with the central set of four bases coming from either a single strand folded around the bases, or several different parallel strands, each contributing one base to the central structure. Nucleic acid sequences which are rich in guanine are capable of forming four-stranded structures called G-quadruplexes (Also known as G-tetrads or G4-DNA). ... Chelation (from Greek χηλή, chelè, meaning claw) is the process of reversible binding (complexation) of a ligand - the chelant, chelator, chelating agent, sequestering agent, or complexing agent - to a metal ion, forming a metal complex, the chelate. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Standard atomic weight 39. ...


In addition to these stacked structures, telomeres also form large loop structures called telomere loops, or T-loops. Here, the single-stranded DNA curls around in a long circle stabilized by telomere-binding proteins.[46] At the very end of the T-loop, the single-stranded telomere DNA is held onto a region of double-stranded DNA by the telomere strand disrupting the double-helical DNA and base pairing to one of the two strands. This triple-stranded structure is called a displacement loop or D-loop.[44]


Chemical modifications

cytosine 5-methylcytosine thymine
Structure of cytosine with and without the 5-methyl group. After deamination the 5-methylcytosine has the same structure as thymine

Download high resolution version (1014x1357, 5 KB) Wikipedia does not have an article with this exact name. ... Image File history File links Size of this preview: 582 × 599 pixelsFull resolution (1202 × 1238 pixel, file size: 5 KB, MIME type: image/png) Chemical structure of 5-methylcytosine. ... Download high resolution version (1269x1363, 6 KB) Wikipedia does not have an article with this exact name. ... Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at... 5-methylcytosine is the methylated form of cytosine. ... For the similarly-spelled vitamin compound, see Thiamine Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ...

Base modifications

Further information: DNA methylation

The expression of genes is influenced by the chromatin structure of a chromosome and regions of heterochromatin (low or no gene expression) correlate with the methylation of cytosine. For example, cytosine methylation, to produce 5-methylcytosine, is important for X-chromosome inactivation.[47] The average level of methylation varies between organisms, with Caenorhabditis elegans lacking cytosine methylation, while vertebrates show higher levels, with up to 1% of their DNA containing 5-methylcytosine.[48] Despite the biological role of 5-methylcytosine it is susceptible to spontaneous deamination to leave the thymine base, and methylated cytosines are therefore mutation hotspots.[49] Other base modifications include adenine methylation in bacteria and the glycosylation of uracil to produce the "J-base" in kinetoplastids.[50][51] DNA methylation is a type of chemical modification of DNA that can be inherited without changing the DNA sequence. ... Chromatin is the complex of DNA and protein found inside the nuclei of eukaryotic cells. ... For differently-colored eyes, see Heterochromia. ... Methylation is a term used in the chemical sciences to denote the attachment or substitution of a methyl group on various substrates. ... Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at... 5-methylcytosine is the methylated form of cytosine. ... In those species in which sex is determined by the presence of the Y or W chromosome rather than the diploidy of the X or Z, a Barr body is the inactive X chromosome in a female cell, or the inactive Z in a male. ... Binomial name Caenorhabditis elegans Maupas, 1900 Caenorhabditis elegans (IPA: ) is a free-living nematode (roundworm), about 1 mm in length, which lives in temperate soil environments. ... This article does not cite any references or sources. ... Deamination is the removal of an amine group from a molecule. ... It has been suggested that mutant be merged into this article or section. ... Glycosylation is the process or result of addition of saccharides to proteins and lipids. ... Orders Trypanosomatida Bodonida The kinetoplastids are a group of flagellate protozoa, including a number of parasites responsible for serious diseases in humans and other animals, as well as various forms found in soil and aquatic environments. ...


DNA damage

Further information: Mutation
Benzopyrene, the major mutagen in tobacco smoke, in an adduct to DNA.[52]

DNA can be damaged by many different sorts of mutagens. These include oxidizing agents, alkylating agents and also high-energy electromagnetic radiation such as ultraviolet light and x-rays. The type of DNA damage produced depends on the type of mutagen. For example, UV light mostly damages DNA by producing thymine dimers, which are cross-links between adjacent pyrimidine bases in a DNA strand.[53] On the other hand, oxidants such as free radicals or hydrogen peroxide produce multiple forms of damage, including base modifications, particularly of guanosine, as well as double-strand breaks.[54] It has been estimated that in each human cell, about 500 bases suffer oxidative damage per day.[55][56] Of these oxidative lesions, the most dangerous are double-strand breaks, as these lesions are difficult to repair and can produce point mutations, insertions and deletions from the DNA sequence, as well as chromosomal translocations.[57] It has been suggested that mutant be merged into this article or section. ... Image File history File links Download high-resolution version (1131x1566, 915 KB)By Richard Wheeler (Zephyris) 2007. ... Image File history File links Download high-resolution version (1131x1566, 915 KB)By Richard Wheeler (Zephyris) 2007. ... Benzo[a]pyrene, C20H12, is a five-ring polycyclic aromatic hydrocarbon that is mutagenic and highly carcinogenic. ... The cigarette is the most common method of smoking tobacco. ... In biology, a mutagen (Latin, literally origin of change) is a physical or chemical agent that changes the genetic information (usually DNA) of an organism and thus increases the number of mutations above the natural background level. ... European Union Chemical hazard symbol for oxidizing agents Dangerous goods label for oxidizing agents Oxidizing agent placard An oxidizing agent (also called an oxidant or oxidizer) is A chemical compound that readily transfers oxygen atoms or A substance that gains electrons in a redox chemical reaction. ... Alkylating agents are so named because of their ability to add alkyl groups to many electronegative groups under conditions present in cells. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... “UV” redirects here. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... A thymine dimer happens when two adjacent thymine residues in a DNA molecule, get chemically bonded to each other. ... In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ... Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in a dilute solution, slightly more viscous than water. ... A point mutation, or substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide. ... An illustration of an insertion at chromosome level At DNA level, an insertion means the insertion of a few base pairs into a genetic sequence. ... A genetic deletion is a genetic aberration in which part of a chromosome is missing. ... Chromosomal translocation of the 4th and 20th chromosome. ...


Many mutagens intercalate into the space between two adjacent base pairs. Intercalators are mostly aromatic and planar molecules, and include ethidium, daunomycin, doxorubicin and thalidomide. In order for an intercalator to fit between base pairs, the bases must separate, distorting the DNA strands by unwinding of the double helix. These structural changes inhibit both transcription and DNA replication, causing toxicity and mutations. As a result, DNA intercalators are often carcinogens, with benzopyrene diol epoxide, acridines, aflatoxin and ethidium bromide being well-known examples.[58][59][60] Nevertheless, due to their properties of inhibiting DNA transcription and replication, they are also used in chemotherapy to inhibit rapidly-growing cancer cells.[61] Intercalation induces structural distortions. ... Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. ... Ethidium bromide - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... Daunorubicin or daunomycin (daunomycin cerubidine) is chemotherapy of the anthracycline family that is given as a treatment for some types of cancer. ... Doxorubicin or Adriamycin® or hydroxyldaunorubicin is a DNA-interacting drug widely used in chemotherapy. ... // Thalidomide is a sedative, hypnotic, and anti-inflammatory medication. ... The hazard symbol for carcinogenic chemicals in the Globally Harmonized System. ... Benzo[a]pyrene, C20H12, is a five-ring polycyclic aromatic hydrocarbon that is mutagenic and highly carcinogenic. ... Acridine, C13H9N, is an organic compound and a nitrogen heterocycle. ... Chemical structure of aflatoxin B1 Aflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus, most notably Aspergillus flavus and Aspergillus parasiticus. ... R-phrases , S-phrases , , , , , Flash point > 100 °C Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Absorption spectrum of ethidium bromide Ethidium bromide (sometimes abbreviated as EtBr) is an intercalating agent commonly used as a nucleic... Chemotherapy is the use of chemical substances to treat disease. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ...


Overview of biological functions

DNA usually occurs as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. The set of chromosomes in a cell makes up its genome; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes.[62] The information carried by DNA is held in the sequence of pieces of DNA called genes. Transmission of genetic information in genes is achieved via complementary base pairing. For example, in transcription, when a cell uses the information in a gene, the DNA sequence is copied into a complementary RNA sequence through the attraction between the DNA and the correct RNA nucleotides. Usually, this RNA copy is then used to make a matching protein sequence in a process called translation which depends on the same interaction between RNA nucleotides. Alternatively, a cell may simply copy its genetic information in a process called DNA replication. The details of these functions are covered in other articles; here we focus on the interactions between DNA and other molecules that mediate the function of the genome. Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... A graphical representation of the normal human karyotype. ... part of a DNA sequence A DNA sequence (sometimes genetic sequence) is a succession of letters representing the primary structure of a real or hypothetical DNA molecule or strand, The possible letters are A, C, G, and T, representing the four nucleotide subunits of a DNA strand (adenine, cytosine, guanine... For a non-technical introduction to the topic, see Introduction to Genetics. ... Genetic transmission is the transfer of genetic information from genes to another generation, or from one location in a cell to another. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ...


Genome structure

Further information: Cell nucleus, Chromatin, Chromosome, Gene, Non-coding DNA

Genomic DNA is located in the cell nucleus of eukaryotes, as well as small amounts in mitochondria and chloroplasts. In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the nucleoid.[63] The genetic information in a genome is held within genes. A gene is a unit of heredity and is a region of DNA that influences a particular characteristic in an organism. Genes contain an open reading frame that can be transcribed, as well as regulatory sequences such as promoters and enhancers, which control the expression of the open reading frame. HeLa cells stained for DNA with the Blue Hoechst dye. ... Chromatin is the complex of DNA and protein found inside the nuclei of eukaryotic cells. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... In genetics, noncoding DNA describes DNA which does not contain instructions for making proteins (or other cell products such as RNAs). ... HeLa cells stained for DNA with the Blue Hoechst dye. ... Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) (from Greek μιτος or mitos, thread + χονδριον or khondrion, granule) is a membrane-enclosed organelle, found in most eukaryotic cells. ... Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... It has been suggested that Genophore be merged into this article or section. ... Heredity (the adjective is hereditary) is the transfer of characteristics from parent to offspring through their genes, or the transfer of a title, style or social status through the social convention known as inheritance (for example, a Hereditary Title may be passed down according to relevant customs and/or laws). ... An open reading frame or ORF is any sequence of DNA or RNA that can be translated into a protein. ... A regulatory sequence (also called regulatory region or ~ element) is a promoter, enhancer or other segment of DNA where regulatory proteins such as transcription factors bind preferentially. ... A promoter is a DNA sequence that contains the information, in the form of DNA sequences, that permits the proper activation or repression of the gene which it controls, i. ... In genetics, an enhancer is a short region of DNA that can be bound with proteins (namely, the trans-acting factors, much like a set of transcription factors) to enhance transcription levels of genes (hence the name) in a gene-cluster. ...


In many species, only a small fraction of the total sequence of the genome encodes protein. For example, only about 1.5% of the human genome consists of protein-coding exons, with over 50% of human DNA consisting of non-coding repetitive sequences.[64] The reasons for the presence of so much non-coding DNA in eukaryotic genomes and the extraordinary differences in genome size, or C-value, among species represent a long-standing puzzle known as the "C-value enigma."[65] However, DNA sequences that do not code protein may still encode functional non-coding RNA molecules, which are involved in the regulation of gene expression.[66] In biology, a species is one of the basic units of biodiversity. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... An exon is any region of DNA within a gene, that is transcribed to the final messenger RNA (mRNA) molecule, rather than being spliced out from the transcribed RNA molecule. ... In the study of DNA sequences, one can distinguish two main types of repeated sequence: Tandem repeats: Satellite DNA, Minisatellite, Microsatellite; Interspersed repeats: SINEs (Short INterspersed Elements), LINEs (Long INterspersed Elements). ... It has been suggested that junk DNA be merged into this article or section. ... Genome size refers to the total amount of DNA contained within one copy of a genome. ... The term C-value refers to the amount of DNA contained within a haploid nucleus (e. ... // Definition and origin The C-value enigma is a term used to describe the complex puzzle surrounding the extensive variation in nuclear genome size among eukaryotic species. ... A non-coding RNA (ncRNA) is any RNA molecule that is not translated into a protein. ...

T7 RNA polymerase (blue) producing a mRNA (green) from a DNA template (orange).
T7 RNA polymerase (blue) producing a mRNA (green) from a DNA template (orange). [67]

Some non-coding DNA sequences play structural roles in chromosomes. Telomeres and centromeres typically contain few genes, but are important for the function and stability of chromosomes.[42][68] An abundant form of non-coding DNA in humans are pseudogenes, which are copies of genes that have been disabled by mutation.[69] These sequences are usually just molecular fossils, although they can occasionally serve as raw genetic material for the creation of new genes through the process of gene duplication and divergence.[70] Image File history File links Size of this preview: 800 × 554 pixelsFull resolution (1348 × 934 pixel, file size: 791 KB, MIME type: image/png) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Size of this preview: 800 × 554 pixelsFull resolution (1348 × 934 pixel, file size: 791 KB, MIME type: image/png) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... T7 RNA Polymerase is an RNA polymerase that catalyzes the formation of RNA in the 5→ 3 direction. ... A telomere is a region of highly repetitive DNA at the end of a chromosome that functions as a disposable buffer. ... The centromere is a region of chromosomes with a special sequence and structure. ... A pseudogene is a nucleotide sequences that is similar to a normal gene, but is not expressed as a functional protein. ... FOSSIL is a standard for allowing serial communication for telecommunications programs under DOS. FOSSIL is an acronym for Fido Opus Seadog Standard Interface Layer. ... Schematic of a region of a chromosome before and after a duplication event Gene duplication occurs when an error in homologous recombination, a retrotransposition event, or duplication of an entire chromosome leads to the duplication of a region of DNA containing a gene [1]. The significance of this process for... Divergent evolution occurs when two or more biological characteristics have a common evolutionary origin but have diverged over evolutionary time. ...


Transcription and translation

Further information: Genetic code, Transcription (genetics), Protein biosynthesis

A gene is a sequence of DNA that contains genetic information and can influence the phenotype of an organism. Within a gene, the sequence of bases along a DNA strand defines a messenger RNA sequence, which then defines a protein sequence. The relationship between the nucleotide sequences of genes and the amino-acid sequences of proteins is determined by the rules of translation, known collectively as the genetic code. The genetic code consists of three-letter 'words' called codons formed from a sequence of three nucleotides (e.g. ACT, CAG, TTT). A series of codons in part of a mRNA molecule. ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... An overview of protein synthesis. ... Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ... The life cycle of an mRNA in a eukaryotic cell. ... Phenylalanine is one of the standard amino acids. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... A series of codons in part of a mRNA molecule. ...


In transcription, the codons of a gene are copied into messenger RNA by RNA polymerase. This RNA copy is then decoded by a ribosome that reads the RNA sequence by base-pairing the messenger RNA to transfer RNA, which carries amino acids. Since there are 4 bases in 3-letter combinations, there are 64 possible codons (43 combinations). These encode the twenty standard amino acids, giving most amino acids more than one possible codon. There are also three 'stop' or 'nonsense' codons signifying the end of the coding region; these are the TAA, TGA and TAG codons. This article does not cite any references or sources. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... It has been suggested that Queuine be merged into this article or section. ... This list of standard proteinogenic amino acids details the chemical structures and properties of the twenty standard amino acids used in proteins by living cells. ...

DNA replication. The double helix is unwound by a helicase and topoisomerase. Next, one DNA polymerase produces the leading strand copy. Another DNA polymerase binds to the lagging strand. This enzyme makes discontinuous segments (called Okazaki fragments) before DNA ligase joins them together.

Image File history File links DNA_replication. ... Image File history File links DNA_replication. ... This article or section does not cite its references or sources. ... Topoisomerase I solves the problem caused by tension generated by winding/unwinding of DNA. It wraps around DNA and makes a cut permitting the helix to spin. ... 3D structure of the DNA-binding helix-hairpin-helix motifs in human DNA polymerase beta A DNA polymerase is an enzyme that assists in DNA replication. ... The leading strand is the DNA strand at the opposite side of the replication fork from the lagging strand. ... In DNA replication, the lagging strand is the DNA strand at the opposite side of the replication fork from the leading strand. ... This article does not cite any references or sources. ... It has been suggested that sticky end/blunt end be merged into this article or section. ...

Replication

Further information: DNA replication

Cell division is essential for an organism to grow, but when a cell divides it must replicate the DNA in its genome so that the two daughter cells have the same genetic information as their parent. The double-stranded structure of DNA provides a simple mechanism for DNA replication. Here, the two strands are separated and then each strand's complementary DNA sequence is recreated by an enzyme called DNA polymerase. This enzyme makes the complementary strand by finding the correct base through complementary base pairing, and bonding it onto the original strand. As DNA polymerases can only extend a DNA strand in a 5′ to 3′ direction, different mechanisms are used to copy the antiparallel strands of the double helix.[71] In this way, the base on the old strand dictates which base appears on the new strand, and the cell ends up with a perfect copy of its DNA. It has been suggested that DNA replicate, Replisome, Replication fork, Lagging strand, Leading strand be merged into this article or section. ... This does not adequately cite its references or sources. ... It has been suggested that DNA replicate, Replisome, Replication fork, Lagging strand, Leading strand be merged into this article or section. ... 3D structure of the DNA-binding helix-hairpin-helix motifs in human DNA polymerase beta A DNA polymerase is an enzyme that assists in DNA replication. ...


Interactions with proteins

All the functions of DNA depend on interactions with proteins. These protein interactions can be non-specific, or the protein can bind specifically to a single DNA sequence. Enzymes can also bind to DNA and of these, the polymerases that copy the DNA base sequence in transcription and DNA replication are particularly important.


DNA-binding proteins

Interaction of DNA with histones (shown in white, top). These proteins' basic amino acids (below left, blue) bind to the acidic phosphate groups on DNA (below right, red).

Structural proteins that bind DNA are well-understood examples of non-specific DNA-protein interactions. Within chromosomes, DNA is held in complexes with structural proteins. These proteins organize the DNA into a compact structure called chromatin. In eukaryotes this structure involves DNA binding to a complex of small basic proteins called histones, while in prokaryotes multiple types of proteins are involved.[72][73] The histones form a disk-shaped complex called a nucleosome, which contains two complete turns of double-stranded DNA wrapped around its surface. These non-specific interactions are formed through basic residues in the histones making ionic bonds to the acidic sugar-phosphate backbone of the DNA, and are therefore largely independent of the base sequence.[74] Chemical modifications of these basic amino acid residues include methylation, phosphorylation and acetylation.[75] These chemical changes alter the strength of the interaction between the DNA and the histones, making the DNA more or less accessible to transcription factors and changing the rate of transcription.[76] Other non-specific DNA-binding proteins found in chromatin include the high-mobility group proteins, which bind preferentially to bent or distorted DNA.[77] These proteins are important in bending arrays of nucleosomes and arranging them into more complex chromatin structures.[78] Image File history File links Nucleosome_2. ... Image File history File links Nucleosome_(opposites_attracts). ... Schematic representation of the assembly of the core histones into the nucleosome. ... Chromatin is the complex of DNA and protein found inside the nuclei of eukaryotic cells. ... Schematic representation of the assembly of the core histones into the nucleosome. ... A nucleosome is a unit made of DNA and histones. ... Electron configurations of lithium and fluorine. ... Methylation is a term used in the chemical sciences to denote the attachment or substitution of a methyl group on various substrates. ... A phosphorylated serine residue Phosphorylation is the addition of a phosphate (PO4) group to a protein or a small molecule or the introduction of a phosphate group into an organic molecule. ... Acetylation describes a reaction, usually with acetic acid, that introduces an acetyl functional group into an organic compound. ... In molecular biology, a transcription factor is a protein that binds DNA at a specific promoter or enhancer region or site, where it regulates transcription. ...


A distinct group of DNA-binding proteins are the single-stranded-DNA-binding proteins that specifically bind single-stranded DNA. In humans, replication protein A is the best-characterised member of this family and is essential for most processes where the double helix is separated, including DNA replication, recombination and DNA repair.[79] These binding proteins seem to stabilize single-stranded DNA and protect it from forming stem loops or being degraded by nucleases. An example of an RNA stem-loop Stem-loop intramolecular base pairing is a pattern that can occur in single-stranded DNA or, more commonly, in RNA. It occurs when two regions of the same molecule base-pair to form a double helix that ends in a short unpaired loop... A nuclease is an enzyme capable of cleaving the phosphodiester bonds between the nucleotide subunits of nucleic acids. ...

The lambda repressor helix-turn-helix transcription factor bound to its DNA target
The lambda repressor helix-turn-helix transcription factor bound to its DNA target[80]

In contrast, other proteins have evolved to specifically bind particular DNA sequences. The most intensively studied of these are the various classes of transcription factors, which are proteins that regulate transcription. Each one of these proteins bind to one particular set of DNA sequences and thereby activates or inhibits the transcription of genes with these sequences close to their promoters. The transcription factors do this in two ways. Firstly, they can bind the RNA polymerase responsible for transcription, either directly or through other mediator proteins; this locates the polymerase at the promoter and allows it to begin transcription.[81] Alternatively, transcription factors can bind enzymes that modify the histones at the promoter; this will change the accessibility of the DNA template to the polymerase.[82] Image File history File links Download high-resolution version (1068x1569, 787 KB) By Richard Wheeler (Zephyris) 2007. ... Image File history File links Download high-resolution version (1068x1569, 787 KB) By Richard Wheeler (Zephyris) 2007. ... The λ repressor of bacteriophage lambda employs a helix-turn-helix to bind DNA. In proteins, the helix-turn-helix (HTH) is a major structural motif capable of binding DNA. It is composed of two α helices joined by a short strand of amino acids and is found in many... In molecular biology, a transcription factor is a protein that binds DNA at a specific promoter or enhancer region or site, where it regulates transcription. ... A promoter is a DNA sequence that contains the information, in the form of DNA sequences, that permits the proper activation or repression of the gene which it controls, i. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ...


As these DNA targets can occur throughout an organism's genome, changes in the activity of one type of transcription factor can affect thousands of genes.[83] Consequently, these proteins are often the targets of the signal transduction processes that mediate responses to environmental changes or cellular differentiation and development. The specificity of these transcription factors' interactions with DNA come from the proteins making multiple contacts to the edges of the DNA bases, allowing them to "read" the DNA sequence. Most of these base-interactions are made in the major groove, where the bases are most accessible.[84] Overview of signal transduction pathways In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in...

The restriction enzyme EcoRV (green) in a complex with its substrate DNA
The restriction enzyme EcoRV (green) in a complex with its substrate DNA[85]

Image File history File links Download high-resolution version (1452x1017, 803 KB) By Richard Wheeler (Zephyris) 2007. ... Image File history File links Download high-resolution version (1452x1017, 803 KB) By Richard Wheeler (Zephyris) 2007. ... A restriction enzyme (or restriction endonuclease) is an enzyme that cuts double-stranded DNA. The enzyme makes two incisions, one through each of the sugar-phosphate backbones (i. ... EcoRV crystal structure complexed with double-stranded DNA EcoRV (pronounced eco R five) is a nuclease enzyme isolated from certain strains of E. coli, In molecular biology, it is a commonly used restriction enzyme. ...

DNA-modifying enzymes

Nucleases and ligases

Nucleases are enzymes that cut DNA strands by catalyzing the hydrolysis of the phosphodiester bonds. Nucleases that hydrolyse nucleotides from the ends of DNA strands are called exonucleases, while endonucleases cut within strands. The most frequently-used nucleases in molecular biology are the restriction endonucleases, which cut DNA at specific sequences. For instance, the EcoRV enzyme shown to the left recognizes the 6-base sequence 5′-GAT|ATC-3′ and makes a cut at the vertical line. In nature, these enzymes protect bacteria against phage infection by digesting the phage DNA when it enters the bacterial cell, acting as part of the restriction modification system.[86] In technology, these sequence-specific nucleases are used in molecular cloning and DNA fingerprinting. Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Hydrolysis is a chemical reaction or process in which a chemical compound reacts with water. ... Diagram of phosphodiester bonds between nucleotides A phosphodiester bond is a group of strong covalent bonds between the phosphorus atom in a phosphate group and two other molecules over two ester bonds. ... Exonucleases are enzymes that cleave nucleotides one at a time from an end of a polynucleotide chain. ... Endonucleases are enzymes that cleave the phosphodiester bond within a nucleotide chain. ... Molecular biology is the study of biology at a molecular level. ... A restriction enzyme (or restriction endonuclease) is an enzyme that cuts double-stranded DNA. The enzyme makes two incisions, one through each of the sugar-phosphate backbones (i. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... This article or section does not cite its references or sources. ... The restriction modification system is used by prokaryotic organisms (i. ... Molecular cloning refers to the procedure of isolating a defined DNA sequence and obtaining multiple copies of it in vivo. ... Genetic fingerprinting or DNA testing is a technique to distinguish between individuals of the same species using only samples of their DNA. Its invention by Sir Alec Jeffreys at the University of Leicester was announced in 1985. ...


Enzymes called DNA ligases can rejoin cut or broken DNA strands, using the energy from either adenosine triphosphate or nicotinamide adenine dinucleotide.[87] Ligases are particularly important in lagging strand DNA replication, as they join together the short segments of DNA produced at the replication fork into a complete copy of the DNA template. They are also used in DNA repair and genetic recombination.[87] It has been suggested that sticky end/blunt end be merged into this article or section. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... Space-filling model of NADH Nicotinamide adenine dinucleotide (NAD+) is an important coenzymes found in cells. ... In DNA replication, the lagging strand is the DNA strand at the opposite side of the replication fork from the leading strand. ... DNA split along the replication fork The replication fork is a structure which forms when DNA is ready to replicate itself. ... DNA damage resulting in multiple broken chromosomes DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. ... Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule. ...


Topoisomerases and helicases

Topoisomerases are enzymes with both nuclease and ligase activity. These proteins change the amount of supercoiling in DNA. Some of these enzyme work by cutting the DNA helix and allowing one section to rotate, thereby reducing its level of supercoiling; the enzyme then seals the DNA break.[27] Other types of these enzymes are capable of cutting one DNA helix and then passing a second strand of DNA through this break, before rejoining the helix.[88] Topoisomerases are required for many processes involving DNA, such as DNA replication and transcription.[28] Topoisomerase I solves the problem caused by tension generated by winding/unwinding of DNA. It wraps around DNA and makes a cut permitting the helix to spin. ... In a relaxed double-helical segment of DNA, the two strands twist around the helical axis once every 10. ...


Helicases are proteins that are a type of molecular motor. They use the chemical energy in nucleoside triphosphates, predominantly ATP, to break hydrogen bonds between bases and unwind the DNA double helix into single strands.[89] These enzymes are essential for most processes where enzymes need to access the DNA bases. This article or section does not cite its references or sources. ... Molecular motors are biological nanomachines and are the essential agents of movement in living organisms. ... Nucleoside triphosphate (NTP) is a nucleotide with three phosphates. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ...


Polymerases

Polymerases are enzymes that synthesise polynucleotide chains from nucleoside triphosphates. They function by adding nucleotides onto the 3′ hydroxyl group of the previous nucleotide in the DNA strand. As a consequence, all polymerases work in a 5′ to 3′ direction.[90] In the active site of these enzymes, the nucleoside triphosphate substrate base-pairs to a single-stranded polynucleotide template: this allows polymerases to accurately synthesise the complementary strand of this template. Polymerases are classified according to the type of template that they use. Nucleoside triphosphate (NTP) is a nucleotide with three phosphates. ... // Hydroxyl group The term hydroxyl group is used to describe the functional group -OH when it is a substituent in an organic compound. ... The active site of an enzyme is the binding site where catalysis occurs. ...


In DNA replication, a DNA-dependent DNA polymerase makes a DNA copy of a DNA sequence. Accuracy is vital in this process, so many of these polymerases have a proofreading activity. Here, the polymerase recognizes the occasional mistakes in the synthesis reaction by the lack of base pairing between the mismatched nucleotides. If a mismatch is detected, a 3′ to 5′ exonuclease activity is activated and the incorrect base removed.[91] In most organisms DNA polymerases function in a large complex called the replisome that contains multiple accessory subunits, such as the DNA clamp or helicases.[92] It has been suggested that DNA replicate, Replisome, Replication fork, Lagging strand, Leading strand be merged into this article or section. ... 3D structure of the DNA-binding helix-hairpin-helix motifs in human DNA polymerase beta A DNA polymerase is an enzyme that assists in DNA replication. ... Proofreading means reading a proof copy of a text in order to detect and correct any errors. ... Exonucleases are enzymes that cleave nucleotides one at a time from an end of a polynucleotide chain. ... The replication of the DNA of E.Coli proceeds via the replisome, a multiprotein workhorse that varies in complexity depending on the organism. ... The assembled human DNA clamp, a trimer of the protein PCNA. A DNA clamp, also known as a sliding clamp, is a protein fold that serves as a processivity-promoting factor in DNA replication. ... This article or section does not cite its references or sources. ...


RNA-dependent DNA polymerases are a specialised class of polymerases that copy the sequence of an RNA strand into DNA. They include reverse transcriptase, which is a viral enzyme involved in the infection of cells by retroviruses, and telomerase, which is required for the replication of telomeres.[93][41] Telomerase is an unusual polymerase because it contains its own RNA template as part of its structure.[42] In biochemistry, a reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase enzyme that transcribes single-stranded RNA into double-stranded DNA. Normal transcription involves the synthesis of RNA from DNA, hence reverse transcription is the reverse of this. ... Groups I: dsDNA viruses II: ssDNA viruses III: dsRNA viruses IV: (+)ssRNA viruses V: (-)ssRNA viruses VI: ssRNA-RT viruses VII: dsDNA-RT viruses A virus (from the Latin noun virus, meaning toxin or poison) is a microscopic particle (ranging in size from 20 - 300 nm) that can infect the... Genera Alpharetrovirus Betaretrovirus Gammaretrovirus Deltaretrovirus Epsilonretrovirus Lentivirus Spumavirus A retrovirus is any virus belonging to the viral family Retroviridae. ... Telomerase is an enzyme that adds specific DNA sequence repeats (TTAGGG in all vertebrates) to the 3 (three prime) end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosomes. ... A telomere is a region of highly repetitive DNA at the end of a chromosome that functions as a disposable buffer. ...


Transcription is carried out by a DNA-dependent RNA polymerase that copies the sequence of a DNA strand into RNA. To begin transcribing a gene, the RNA polymerase binds to a sequence of DNA called a promoter and separates the DNA strands. It then copies the gene sequence into a messenger RNA transcript until it reaches a region of DNA called the terminator, where it halts and detaches from the DNA. As with human DNA-dependent DNA polymerases, RNA polymerase II, the enzyme that transcribes most of the genes in the human genome, operates as part of a large protein complex with multiple regulatory and accessory subunits.[94] This article does not cite any references or sources. ... A promoter is a DNA sequence that contains the information, in the form of DNA sequences, that permits the proper activation or repression of the gene which it controls, i. ... The life cycle of an mRNA in a eukaryotic cell. ... In genetics, a terminator marks the end of a gene on the DNA for transcription. ...


Genetic recombination

Structure of the Holliday junction intermediate in genetic recombination. The four separate DNA strands are coloured red, blue, green and yellow.[95]
Further information: Genetic recombination
Recombination involves the breakage and rejoining of two chromosomes (M and F) to produce two re-arranged chromosomes (C1 and C2).
Recombination involves the breakage and rejoining of two chromosomes (M and F) to produce two re-arranged chromosomes (C1 and C2).

A DNA helix does not usually interact with other segments of DNA, and in human cells the different chromosomes even occupy separate areas in the nucleus called "chromosome territories".[96] This physical separation of different chromosomes is important for the ability of DNA to function as a stable repository for information, as one of the few times chromosomes interact is during chromosomal crossover when they recombine. Chromosomal crossover is when two DNA helices break, swap a section and then rejoin. Image File history File links Holliday_Junction_cropped. ... Image File history File links Download high-resolution version (1620x1620, 689 KB)By Richard Wheeler (Zephyris) 2007. ... A Holliday junction is a mobile junction between four strands of DNA. The structure is named after Robin Holliday, who proposed it in 1964 to account for a particular type of exchange of genetic information in yeast known as homologous recombination. ... Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule. ... Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule. ... Image File history File links Chromosomal_Recombination. ... Image File history File links Chromosomal_Recombination. ... Thomas Hunt Morgans illustration of crossing over (1916) Homologous Recombination is the process by which two chromosomes, paired up during prophase I of meiosis, exchange some distal portion of their DNA. Crossover occurs when two chromosomes, normally two homologous instances of the same chromosome, break and then reconnect but... Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule. ...


Recombination allows chromosomes to exchange genetic information and produces new combinations of genes, which increases the efficiency of natural selection and can be important in the rapid evolution of new proteins.[97] Genetic recombination can also be involved in DNA repair, particularly in the cell's response to double-strand breaks.[98] Darwins illustrations of beak variation in the finches of the Galápagos Islands, which hold 13 closely related species that differ most markedly in the shape of their beaks. ...


The most common form of chromosomal crossover is homologous recombination, where the two chromosomes involved share very similar sequences. Non-homologous recombination can be damaging to cells, as it can produce chromosomal translocations and genetic abnormalities. The recombination reaction is catalyzed by enzymes known as recombinases, such as RAD51.[99] The first step in recombination is a double-stranded break either caused by an endonuclease or damage to the DNA.[100] A series of steps catalyzed in part by the recombinase then leads to joining of the two helices by at least one Holliday junction, in which a segment of a single strand in each helix is annealed to the complementary strand in the other helix. The Holliday junction is a tetrahedral junction structure that can be moved along the pair of chromosomes, swapping one strand for another. The recombination reaction is then halted by cleavage of the junction and re-ligation of the released DNA.[101] Chromosomal crossover is the process by which two chromosomes, paired up during Prophase I of meiosis, exchange some distal portion of their DNA. Crossover occurs when two chromosomes, normally two homologous instances of the same chromosome, break and then reconnect but to the different end piece. ... Chromosomal translocation of the 4th and 20th chromosome. ... Rad51 is the eukaryotic homolog of the prokaryotic RecA protein. ... Endonucleases are enzymes that cleave the phosphodiester bond within a nucleotide chain. ... A Holliday junction is a mobile junction between four strands of DNA. The structure is named after Robin Holliday, who proposed it in 1964 to account for a particular type of exchange of genetic information in yeast known as homologous recombination. ...


Evolution of DNA-based metabolism

DNA contains the genetic information that allows all modern living things to function, grow and reproduce. However, it is unclear how long in the 4-billion-year history of life DNA has performed this function, as it has been proposed that the earliest forms of life may have used RNA as their genetic material.[90][102] RNA may have acted as the central part of early cell metabolism as it can both transmit genetic information and carry out catalysis as part of ribozymes.[103] This ancient RNA world where nucleic acid would have been used for both catalysis and genetics may have influenced the evolution of the current genetic code based on four nucleotide bases. This would occur since the number of unique bases in such an organism is a trade-off between a small number of bases increasing replication accuracy and a large number of bases increasing the catalytic efficiency of ribozymes.[104] This timeline of the evolution of life outlines the major events in the development of life on the planet Earth. ... In chemistry and biology, catalysis is the acceleration (increase in rate) of a chemical reaction by means of a substance, called a catalyst, that is itself not consumed by the overall reaction. ... // A ribozyme (from ribonucleic acid enzyme, also called RNA enzyme or catalytic RNA) is an RNA molecule that catalyzes a chemical reaction. ... RNA with its nitrogenous bases to the left and DNA to the right. ...


Unfortunately, there is no direct evidence of ancient genetic systems, as recovery of DNA from most fossils is impossible. This is because DNA will survive in the environment for less than one million years and slowly degrades into short fragments in solution.[105] Although claims for older DNA have been made, most notably a report of the isolation of a viable bacterium from a salt crystal 250-million years old,[106] these claims are controversial and have been disputed.[107][108]


Uses in technology

Genetic engineering

Further information: Molecular biology and genetic engineering

Modern biology and biochemistry make intensive use of recombinant DNA technology. Recombinant DNA is a man-made DNA sequence that has been assembled from other DNA sequences. They can be transformed into organisms in the form of plasmids or in the appropriate format, by using a viral vector.[109] The genetically modified organisms produced can be used to produce products such as recombinant proteins, used in medical research,[110] or be grown in agriculture.[111][112] Molecular biology is the study of biology at a molecular level. ... An iconic image of genetic engineering; this autoluminograph from 1986 of a glowing transgenic tobacco plant bearing the luciferase gene, illustrating the possibilities of genetic engineering. ... This article needs additional references or sources for verification. ... Biochemistry is the study of the chemical processes and transformations in living organisms. ... Recombinant DNA (rDNA) is an artificial DNA sequence resulting from the combination of different DNA sequences. ... It has been suggested that this article or section be merged into Transfection. ... Figure 1 : Schematic drawing of a bacterium with plasmids enclosed. ... Viral vectors are a tool commonly used by biologists to deliver genetic material into cells inside a living organism or cultured in vitro. ... An iconic image of genetic engineering; this autoluminograph from 1986 of a glowing transgenic tobacco plant bearing the luciferase gene, illustrating the possibilities of genetic engineering. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...


Forensics

Further information: Genetic fingerprinting

Forensic scientists can use DNA in blood, semen, skin, saliva or hair at a crime scene to identify a perpetrator. This process is called genetic fingerprinting, or more accurately, DNA profiling. In DNA profiling, the lengths of variable sections of repetitive DNA, such as short tandem repeats and minisatellites, are compared between people. This method is usually an extremely reliable technique for identifying a criminal.[113] However, identification can be complicated if the scene is contaminated with DNA from several people.[114] DNA profiling was developed in 1984 by British geneticist Sir Alec Jeffreys,[115] and first used in forensic science to convict Colin Pitchfork in the 1988 Enderby murders case.[116] People convicted of certain types of crimes may be required to provide a sample of DNA for a database. This has helped investigators solve old cases where only a DNA sample was obtained from the scene. DNA profiling can also be used to identify victims of mass casualty incidents.[117] Genetic fingerprinting, DNA testing, DNA typing, and DNA profiling are techniques used to distinguish between individuals of the same species using only samples of their DNA. Its invention by Sir Alec Jeffreys at the University of Leicester was announced in 1985. ... Crime Scene, done by the United States Army Criminal Investigation Command Forensic science (often shortened to forensics) is the application of a broad spectrum of sciences to answer questions of interest to the legal system. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... Horse semen being collected for breeding purposes. ... Beyond overall skin structure, refer below to: See-also. ... Saliva is the watery and usually somewhat frothy substance produced in the mouths of humans and some animals. ... For the film, see Hair (film). ... Genetic fingerprinting, DNA testing, DNA typing, and DNA profiling are techniques used to distinguish between individuals of the same species using only samples of their DNA. Its invention by Sir Alec Jeffreys at the University of Leicester was announced in 1985. ... A short tandem repeat (STR) in DNA is a class of polymorphisms that occurs when a pattern of two or more nucleotides are repeated and the repeated sequences are directly adjacent to each other. ... A minisatellite is a section of DNA that consists of a short series of bases 10-100bp, these occur at more than 1000 locations in the Genome. ... Professor Sir Alec John Jeffreys, FRS, (born in 9 January 1950 at Luton in Bedfordshire) is a British geneticist, who developed techniques for DNA fingerprinting and DNA profiling. ... Colin Pitchfork Colin Pitchfork (born c. ...


Bioinformatics

Further information: Bioinformatics

Bioinformatics involves the manipulation, searching, and data mining of DNA sequence data. The development of techniques to store and search DNA sequences have led to widely-applied advances in computer science, especially string searching algorithms, machine learning and database theory.[118] String searching or matching algorithms, which find an occurrence of a sequence of letters inside a larger sequence of letters, were developed to search for specific sequences of nucleotides.[119] In other applications such as text editors, even simple algorithms for this problem usually suffice, but DNA sequences cause these algorithms to exhibit near-worst-case behaviour due to their small number of distinct characters. The related problem of sequence alignment aims to identify homologous sequences and locate the specific mutations that make them distinct. These techniques, especially multiple sequence alignment, are used in studying phylogenetic relationships and protein function.[120] Data sets representing entire genomes' worth of DNA sequences, such as those produced by the Human Genome Project, are difficult to use without annotations, which label the locations of genes and regulatory elements on each chromosome. Regions of DNA sequence that have the characteristic patterns associated with protein- or RNA-coding genes can be identified by gene finding algorithms, which allow researchers to predict the presence of particular gene products in an organism even before they have been isolated experimentally.[121] Map of the human X chromosome (from the NCBI website). ... Map of the human X chromosome (from the NCBI website). ... Data mining has been defined as the nontrivial extraction of implicit, previously unknown, and potentially useful information from data [1] and the science of extracting useful information from large data sets or databases [2]. Data mining involves sorting through large amounts of data and picking out relevant information. ... Computer science, or computing science, is the study of the theoretical foundations of information and computation and their implementation and application in computer systems. ... String searching algorithms are an important class of string algorithms that try to find a place where one or several strings (also called patterns) are found within a larger string or text. ... As a broad subfield of artificial intelligence, machine learning is concerned with the design and development of algorithms and techniques that allow computers to learn. At a general level, there are two types of learning: inductive, and deductive. ... A database is an information set with a regular structure. ... Notepad is the standard text editor for Microsoft Windows A text editor is a piece of computer software for editing plain text. ... In bioinformatics, a sequence alignment is a way of arranging the primary sequences of DNA, RNA, or protein to identify regions of similarity that may be a consequence of functional, structural, or evolutionary relationships between the sequences. ... In biology, homology is any similarity between structures that is due to their shared ancestry. ... It has been suggested that mutant be merged into this article or section. ... First 90 positions of a protein multiple sequence alignment of instances of the acidic ribosomal protein P0 (L10E) from several organisms. ... Phylogenetic groups, or taxa, can be monophyletic, paraphyletic, or polyphyletic. ... // The Human Genome Project (HGP) is a project to de-code (i. ... Gene finding is the area of computational biology that is concerned with algorithmically identifying stretches of sequence, usually genomic DNA, that are biologically functional. ... A gene product is the biochemical material, either RNA or protein, resulting from expression of a gene. ...


DNA and computation

Further information: DNA computing

DNA was first used in computing to solve a small version of the directed Hamiltonian path problem, an NP-complete problem.[122] DNA computing is advantageous over electronic computers in power use, space use, and efficiency, due to its ability to compute in a highly parallel fashion (see parallel computing). A number of other problems, including simulation of various abstract machines, the boolean satisfiability problem, and the bounded version of the travelling salesman problem, have since been analysed using DNA computing.[123] Due to its compactness, DNA also has a theoretical role in cryptography, where in particular it allows unbreakable one-time pads to be efficiently constructed and used.[124] DNA computing is a form of computing which uses DNA and molecular biology, instead of the traditional silicon-based computer technologies. ... In the mathematical field of graph theory the Hamiltonian path problem and the Hamiltonian cycle problem are problems of determining whether a Hamiltonian path or a Hamiltonian cycle exists in a given graph (whether directed or undirected). ... In complexity theory, the NP-complete problems are the most difficult problems in NP, in the sense that they are the ones most likely not to be in P. The reason is that if you could find a way to solve an NP-complete problem quickly, then you could use... DNA computing is a form of computing which uses DNA and molecular biology, instead of the traditional silicon-based computer technologies. ... Parallel computing is the simultaneous execution of the same task (split up and specially adapted) on multiple processors in order to obtain results faster. ... An abstract machine, also called an abstract computer, is a theoretical model of a computer hardware or software system used in Automata theory. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... If a salesman starts at point A, and if the distances between every pair of points are known, what is the shortest route which visits all points and returns to point A? The traveling salesman problem (TSP) is a problem in discrete or combinatorial optimization. ... The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κρυπτός kryptós hidden, and the verb γράφω gráfo write or λεγειν legein to speak) is the study of message secrecy. ... Excerpt from a one-time pad. ...


History and anthropology

Further information: Phylogenetics and Genetic genealogy

Because DNA collects mutations over time, which are then inherited, it contains historical information and by comparing DNA sequences, geneticists can infer the evolutionary history of organisms, their phylogeny.[125] This field of phylogenetics is a powerful tool in evolutionary biology. If DNA sequences within a species are compared, population geneticists can learn the history of particular populations. This can be used in studies ranging from ecological genetics to anthropology; for example, DNA evidence is being used to try to identify the Ten Lost Tribes of Israel.[126][127] Phylogenetic groups, or taxa, can be monophyletic, paraphyletic, or polyphyletic. ... Genetic genealogy is the application of genetics to traditional genealogy. ... In biology, phylogenetics (Greek: phylon = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e. ... Phylogenetic groups, or taxa, can be monophyletic, paraphyletic, or polyphyletic. ... This article or section does not cite any references or sources. ... Population genetics is the study of the distribution of and change in allele frequencies under the influence of the four evolutionary forces: natural selection, genetic drift, mutation, and migration. ... Ecological genetics is the study of genetics (itself a field of biology) from an ecological perspective. ... Anthropology (from Greek: ἀνθρωπος, anthropos, human being; and λόγος, logos, knowledge) is the comparative study of the physical and social characteristics of humanity through the examination of historical and present geographical distribution, cultural history, acculturation, and cultural relationships. ... The Ten Lost Tribes of Israel are the ancient Tribes of Israel that disappear from the Biblical account after the Kingdom of Israel was totally destroyed, enslaved and exiled by ancient Assyria. ...


DNA has also been used to look at modern family relationships, such as establishing family relationships between the descendants of Sally Hemings and Thomas Jefferson. This usage is closely related to the use of DNA in criminal investigations detailed above. Indeed, some criminal investigations have been solved when DNA from crime scenes has matched relatives of the guilty individual.[128] Sally Hemings (Shadwell, Albemarle County, Virginia, circa 1773 or 1773 – Charlottesville, Virginia, 1835) was a quadroon slave owned by Thomas Jefferson. ... Thomas Jefferson (13 April 1743 N.S.–4 July 1826) was the third President of the United States (1801–09), the principal author of the Declaration of Independence (1776), and one of the most influential Founding Fathers for his promotion of the ideals of Republicanism in the United States. ...


History

Further information: History of molecular biology

DNA was first isolated by the Swiss physician Friedrich Miescher who, in 1869, discovered a microscopic substance in the pus of discarded surgical bandages. As it resided in the nuclei of cells, he called it "nuclein".[129] In 1919 this discovery was followed by Phoebus Levene's identification of the base, sugar and phosphate nucleotide unit.[130] Levene suggested that DNA consisted of a string of nucleotide units linked together through the phosphate groups. However, Levene thought the chain was short and the bases repeated in a fixed order. In 1937 William Astbury produced the first X-ray diffraction patterns that showed that DNA had a regular structure.[131] Image File history File links Download high-resolution version (1500x1118, 919 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): DNA ... Image File history File links Download high-resolution version (1500x1118, 919 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): DNA ... Francis Harry Compton Crick OM FRS (8 June 1916 – 28 July 2004) was an English molecular biologist, physicist, and neuroscientist, who is most noted for being one of the co-discoverers of the structure of the DNA molecule in 1953. ... Image File history File links Download high-resolution version (963x1200, 119 KB) James D. Watson, source: http://www. ... Image File history File links Download high-resolution version (963x1200, 119 KB) James D. Watson, source: http://www. ... James Dewey Watson born April 6, 1928) is an American molecular biologist, best known as one of the co-discoverers of the structure of the DNA molecule. ... The history of molecular biology begins in the 1930s with the convergence of various, previously distinct biological disciplines: biochemistry, genetics, microbiology, and virology. ... Friedrich Miescher Basel, - 26 August 1895, Davos) was a Swiss biologist. ... Pus is a whitish-yellow or yellow substance produced during inflammatory responses of the body that can be found in regions of pyogenic bacterial infections. ... Molecular diagram of a hypothetical tetranucleotide, as proposed (incorrectly) by Phoebus Levene around 1910. ... William Astbury (1898-1961) was an English biochemist who made X-ray diffraction studies of nucleic acid in 1937. ... X-ray crystallography is a technique in crystallography in which the pattern produced by the diffraction of x-rays through the closely spaced lattice of atoms in a crystal is recorded and then analyzed to reveal the nature of that lattice. ...


In 1943, Oswald Theodore Avery discovered that traits of the "smooth" form of the Pneumococcus could be transferred to the "rough" form of the same bacteria by mixing killed "smooth" bacteria with the live "rough" form. Avery identified DNA as this transforming principle.[132] DNA's role in heredity was confirmed in 1953, when Alfred Hershey and Martha Chase in the Hershey-Chase experiment showed that DNA is the genetic material of the T2 phage.[133] Oswald Avery in 1937 Oswald Theodore Avery ( 1877- 1955) was a physician, medical researcher and early molecular biologist. ... In biology, a trait or character is a feature of an organism. ... Griffiths experiment was conducted in 1928 by Frederick Griffith which was one of the first experiments suggesting that bacteria are capable of transferring genetic information, otherwise known as the “transforming principle”, which was later discovered to be DNA. Griffith used two strains of Pneumococcus (which infects mice... Heredity (the adjective is hereditary) is the transfer of characteristics from parent to offspring through their genes, or the transfer of a title, style or social status through the social convention known as inheritance (for example, a Hereditary Title may be passed down according to relevant customs and/or laws). ... Alfred Day Hershey (December 4, 1908 – May 22, 1997) was an American Nobel Prize-winning bacteriologist. ... Martha Cowles Chase (1927 – 2003) was a young laboratory assistant in the early 1950s when she and Alfred Hershey conducted one of the most famous experiments in 20th century biology. ... The Hershey-Chase experiment was a series of experiments conducted in 1952 by Alfred Hershey and Martha Chase. ... Genetic material is used to store the genetic information of an organic life form. ... Enterobacteria phage T2 is a virulent bacteriophage of the T4-like viruses genus, in the family Myoviridae. ...


In 1953, based on X-ray diffraction images[134] taken by Rosalind Franklin and the information that the bases were paired, James D. Watson and Francis Crick suggested[134] what is now accepted as the first accurate model of DNA structure in the journal Nature.[5] Experimental evidence for Watson and Crick's model were published in a series of five articles in the same issue of Nature.[135] Of these, Franklin and Raymond Gosling's paper[136] saw the publication of the X-ray diffraction image[137], which was key in the Watson and Crick interpretation, as well as another article, co-authored by Maurice Wilkins and his colleagues.[138] Franklin and Gosling's subsequent paper identified the distinctions between the A and B structures of the double helix in DNA.[139] In 1962 Watson, Crick, and Maurice Wilkins jointly received the Nobel Prize in Physiology or Medicine (Franklin didn't share the prize with them since she had died earlier).[140] However, there remains some speculation on who should have received credit for the scientific breakthrough since it had been discovered that the Watson-Crick findings were based on Franklin's data. Furthermore, Watson and Crick later claimed that, only long after Franklin's death, they could not have discovered the double helix of DNA in the early months of 1953 without her work. Photo 51, an X-ray diffraction image of sodium salt of DNA. B configuration Photo 51 is the name given to an X-ray diffraction image of DNA taken by Rosalind Franklin in 1952[1] that was critical evidence[2] in identifying the structure of DNA.[3] The photo was... Rosalind Elsie Franklin (25 July 1920 – 16 April 1958) was an English physical chemist and crystallographer who made important contributions to the understanding of the fine structures of DNA, viruses, coal and graphite. ... James Dewey Watson born April 6, 1928) is an American molecular biologist, best known as one of the co-discoverers of the structure of the DNA molecule. ... Francis Harry Compton Crick OM FRS (8 June 1916 – 28 July 2004) was an English molecular biologist, physicist, and neuroscientist, who is most noted for being one of the co-discoverers of the structure of the DNA molecule in 1953. ... The Discovery of the DNA Double Helix Molecular structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid by James D. Watson and Francis H. Crick. ... Nature is one of the most prominent scientific journals, first published on 4 November 1869. ... Rosalind Elsie Franklin (25 July 1920 – 16 April 1958) was an English physical chemist and crystallographer who made important contributions to the understanding of the fine structures of DNA, viruses, coal and graphite. ... The joke funeral card in the names of Rosalind Franklin and Raymond Gosling Raymond Gosling is a distinguished scientist who worked with both Maurice Wilkins and Rosalind Franklin at Kings College London in deducing the structure of DNA. He was born in 1926 and attended school in Wembley. ... This article does not cite its references or sources. ... This article does not cite its references or sources. ... Nobel Prize medal. ... List of Nobel Prize laureates in Physiology or Medicine from 1901 to the present day. ...


In an influential presentation in 1957, Crick laid out the "Central Dogma" of molecular biology, which foretold the relationship between DNA, RNA, and proteins, and articulated the "adaptor hypothesis".[141] Final confirmation of the replication mechanism that was implied by the double-helical structure followed in 1958 through the Meselson-Stahl experiment.[142] Further work by Crick and coworkers showed that the genetic code was based on non-overlapping triplets of bases, called codons, allowing Har Gobind Khorana, Robert W. Holley and Marshall Warren Nirenberg to decipher the genetic code.[143] These findings represent the birth of molecular biology. Information flow in biological systems The central dogma of molecular biology was first enunciated by Francis Crick in 1958[1] and re-stated in a Nature paper published in 1970:[2] POSTLEWAITE IS A TOOL The central dogma of molecular biology deals with the detailed residue-by-residue transfer of... A summary of the three postulated methods of DNA synthesis The Meselson-Stahl experiment was an experiment by Matthew Meselson and Franklin Stahl to prove that DNA replication was semiconservative. ... Har Gobind Khorana (born January 9, 1922) is of Punjabi origin, a Nobel Prize laureate and a molecular biologist. ... Robert W. Holley, the structure of a tRNA is shown in the background Dr Robert W. Holley (January 28, 1922 - February 11, 1993) was an American biochemist, he was awarded the Nobel Prize in Physiology or Medicine in 1968 for describing the structure of alanine transfer RNA, linking DNA and... Marshall Nirenberg Marshall Warren Nirenberg (born April 10, 1927) is a U.S. biochemist and geneticist. ... A series of codons in part of a mRNA molecule. ... Molecular biology is the study of biology at a molecular level. ...


See also

A genetic disorder is a disease caused by abnormalities in genes or chromosomes. ... Figure 1: Schematic drawing of a bacterium with plasmids enclosed. ... The term DNA sequencing encompasses biochemical methods for determining the order of the nucleotide bases, adenine, guanine, cytosine, and thymine, in a DNA oligonucleotide. ... A Southern blot is a method routinely used in molecular biology to check for the presence of a DNA sequence in a DNA sample. ... It has been suggested that Gene chip technology be merged into this article or section. ... PCR tubes in a stand after a colony PCR The polymerase chain reaction (PCR) is a biochemistry and molecular biology technique[1] for exponentially amplifying DNA, via enzymatic replication, without using a living organism (such as E. coli or yeast). ... Nucleoside phosphoramidites are used to synthesise short nucleic acid chains. ... In molecular biology, junk DNA is a collective label for the portions of the DNA sequence of a chromosome or a genome for which no function has yet been identified. ...

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A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Nova is a popular science television series from the USA produced by WGBH and can be seen on PBS and in more than 100 countries. ...

Further reading

  • Clayton, Julie. (Ed.). 50 Years of DNA, Palgrave MacMillan Press, 2003. ISBN 978-1-40-391479-8
  • Judson, Horace Freeland. The Eighth Day of Creation: Makers of the Revolution in Biology, Cold Spring Harbor Laboratory Press, 1996. ISBN 978-0-87-969478-4
  • Olby, Robert. The Path to The Double Helix: Discovery of DNA, first published in October 1974 by MacMillan, with foreword by Francis Crick; ISBN 978-0-48-668117-7; the definitive DNA textbook, revised in 1994, with a 9 page postscript.
  • Ridley, Matt. Francis Crick: Discoverer of the Genetic Code (Eminent Lives) HarperCollins Publishers; 192 pp, ISBN 978-0-06-082333-7 2006
  • Rose, Steven. The Chemistry of Life, Penguin, ISBN 978-0-14-027273-4.
  • Watson, James D. and Francis H.C. Crick. A structure for Deoxyribose Nucleic Acid (PDF). Nature 171, 737–738, 25 April 1953.
  • Watson, James D. DNA: The Secret of Life ISBN 978-0-375-41546-3.
  • Watson, James D. The Double Helix: A Personal Account of the Discovery of the Structure of DNA (Norton Critical Editions). ISBN 978-0-393-95075-5
  • Watson, James D. "Avoid boring people and other lessons from a life in science" New York: Random House. ISBN 978-0-375-421844
  • Calladine, Chris R.; Drew, Horace R.; Luisi, Ben F. and Travers, Andrew A. Understanding DNA, Elsevier Academic Press, 2003. ISBN 978-0-12155089-9

Robert Olby is a professor in the Department of History and Philosophy of Science at the University of Pittsburgh. ... Matthew (Matt) Ridley (born February 7, 1958 at Newcastle upon Tyne) (not to be confused with Mark Ridley) is an English science writer. ... Nature is one of the most prominent scientific journals, first published on 4 November 1869. ... is the 115th day of the year (116th in leap years) in the Gregorian calendar. ... Year 1953 (MCMLIII) was a common year starting on Thursday (link will display full calendar) of the Gregorian calendar. ... James Watson The Double Helix: A Personal Account of the Discovery of the Structure of DNA is an autobiographical account of the discovery of structure of DNA. It was written by James D. Watson and published in 1968. ...

External links

Molecular and Cellular Biology Portal
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v  d  e
Major families of biochemicals
Peptides | Amino acids | Nucleic acids | Carbohydrates | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides
Analogues of nucleic acids: Types of Nucleic Acids Analogues of nucleic acids:
Nucleobases: Purine (Adenine, Guanine) | Pyrimidine (Uracil, Thymine, Cytosine)
Nucleosides: Adenosine/Deoxyadenosine | Guanosine/Deoxyguanosine | Uridine | Thymidine | Cytidine/Deoxycytidine
Nucleotides: monophosphates (AMP, UMP, GMP, CMP) | diphosphates (ADP, UDP, GDP, CDP) | triphosphates (ATP, UTP, GTP, CTP) | cyclic (cAMP, cGMP, cADPR)
Deoxynucleotides: monophosphates (dAMP, TMP, dGMP, dCMP) | diphosphates (dADP, TDP, dGDP, dCDP) | triphosphates (dATP, TTP, dGTP, dCTP)
Ribonucleic acids: RNA | mRNA | piRNA | tRNA | rRNA | ncRNA | gRNA | shRNA | siRNA | snRNA | miRNA | snoRNA
Deoxyribonucleic acids: DNA | mtDNA | cDNA | plasmid | Cosmid | BAC | YAC | HAC
Analogues of nucleic acids: GNA | PNA | TNA | Morpholino | LNA

Biochemistry is the study of the chemical processes and transformations in living organisms. ... Peptides (from the Greek πεπτος, digestible), are the family of short molecules formed from the linking, in a defined order, of various α-amino acids. ... Phenylalanine is one of the standard amino acids. ... Look up nucleic acid in Wiktionary, the free dictionary. ... Lactose is a disaccharide found in milk. ... A polyunsaturated triglyceride. ... Many terpenes are derived from conifer resins, here a pine. ... The orange ring surrounding Grand Prismatic Spring is due to carotenoid molecules, produced by huge mats of algae and bacteria. ... Polypyrrole A Polypyrrole (PPy) is a chemical compound formed from a number of connected pyrrole ring structures. ... A cofactor is any substance that needs to be present in addition to an enzyme to catalyze a certain reaction. ... Steroid skeleton of lanosterol. ... Molecular structure of flavone The term flavonoid refers to a class of plant secondary metabolites based around a phenylbenzopyrone structure. ... Chemical structure of ephedrine, a phenethylamine alkaloid An alkaloid is, strictly speaking, a naturally occurring amine produced by a plant,[1] but amines produced by animals and fungi are also called alkaloids. ... Polyketides are secondary metabolites from bacteria, fungi, plants, and animals. ... A glycoside is a molecule where a sugar group is bonded through its anomeric carbon to a nonsugar group by either an oxygen or a nitrogen atom. ... Look up nucleic acid in Wiktionary, the free dictionary. ... Adenine Guanine Thymine Cytosine ... Purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. ... This article or section does not adequately cite its references or sources. ... Guanine is one of the five main nucleobases found in the nucleic acids DNA and RNA; the others being adenine, cytosine, thymine, and uracil. ... Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring [1]. It is isomeric with two other forms of diazine. ... Uracil is a pyrimidine which is common and naturally occurring. ... For the similarly-spelled vitamin compound, see Thiamine Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ... Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at... Nucleosides are glycosylamines made by attaching a nucleobase (often reffered to simply as bases) to a ribose ring. ... Adenosine is a nucleoside comprised of adenine attached to a ribose (ribofuranose) moiety via a β-N9-glycosidic bond. ... The chemical structure of adenosine Adenosine is a nucleoside formed when adenine is attached to a ribose ring (also known as a ribofuranose) via a β-N9-glycosidic bond. ... The chemical structure of Guanosine Guanosine is a nucleoside comprising guanine attached to a ribose (ribofuranose) ring via a β-N9-glycosidic bond. ... Guanosine is a molecule (known as a nucleoside) that is formed when guanine is attached to a ribose ring (also known as a ribofuranose) via a β-N9-glycosidic bond. ... Uridine is a molecule (known as a nucleoside) that is formed when uracil is attached to a ribose ring (also known as a ribofuranose) via a β-N1-glycosidic bond. ... The chemical structure of deoxythymidine Thymidine (more precisely called deoxythymidine can also be labelled deoxyribosylthymine, and thymine deoxyriboside) is a chemical compound, more precisely a pyrimidine deoxynucleoside. ... Cytidine is a molecule (known as a nucleoside) that is formed when cytosine is attached to a ribose ring (also known as a ribofuranose) via a β-N1-glycosidic bond. ... Cytidine is a molecule (known as a nucleoside) that is formed when cytosine is attached to a ribose ring (also known as a ribofuranose) via a β-N1-glycosidic bond. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... Adenosine monophosphate, also known as 5-adenylic acid and abbreviated AMP, is a nucleotide that is found in RNA. It is an ester of phosphoric acid with the nucleoside adenosine. ... Uridine monophosphate, also known as 5-uridylic acid and abbreviated UMP, is a nucleotide that is found in RNA. It is an ester of phosphoric acid with the nucleoside uridine. ... Guanosine monophosphate, also known as 5-guanidylic acid and abbreviated GMP, is a nucleotide that is found in RNA. It is an ester of phosphoric acid with the nucleoside guanosine. ... Cytidine monophosphate, also known as 5-cytidylic acid and abbreviated CMP, is a nucleotide that is found in RNA. It is an ester of phosphoric acid with the nucleoside cytidine. ... Adenosine diphosphate, abbreviated ADP, is a nucleotide. ... Uridine diphosphate, abbreviated UDP, is a nucleotide. ... Cytidine diphosphate, abbreviated CDP, is a nucleotide. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide primarily known in biochemistry as the molecular currency of intracellular energy transfer. ... Guanosine triphosphate (GTP) is also known as guanosine-5-triphosphate. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide primarily known in biochemistry as the molecular currency of intracellular energy transfer. ... Structure of cAMP cAMP represented in three ways, the left with sticks-representation, the middle with structure formula, and the right with space filled representation. ... Cyclic guanosine monophosphate (cGMP) is a second messenger derived from GTP. Cyclic guanosine monophosphate (cGMP) is a cyclic nucleotide derived from guanosine triphosphate (GTP). ... Cyclic ADP Ribose popularly known as cADPR is a cyclic adenine nucleotide (like cAMP) with two phosphate groups present on 5 OH of the adenosine (like ADP), further connected to another ribose at the 5 position which in turn closes the cycle by glycosidic bonding to the Nitrogen1 of the... A nucleotide is a monomer or the structural unit of nucleotide chains forming nucleic acids as RNA and DNA. A nucleotide consists of a heterocyclic nucleobase, a pentose sugar, and a phosphate or polyphosphate group. ... This article belongs in one or more categories. ... Thymidine monophosphate, also known as 5-thymidylic acid and abbreviated TMP, is a nucleotide that is found in RNA. It is an ester of phosphoric acid with the nucleoside thymidine. ... Deoxyguanosine monophosphate is a derivative of the common nucleic acid GTP, or guanosine triphosphate, in which the -OH (hydroxyl) group on the 2 carbon on the nucleotides pentose has been reduced to just a hydrogen atom (hence the deoxy- part of the name). ... Deoxycytidine monophosphate is a deoxynucleotide, and one of the four monomers that make up DNA. In a DNA double helix, it will base pair with deoxyguanosine monophosphate. ... Deoxyadenosine diphosphate is a derivative of the common nucleic acid ATP, or adenosine triphosphate, in which the -OH (hydroxyl) group on the 2 carbon on the nucleotides pentose has been removed (hence the deoxy- part of the name). ... Thymidine diphosphate, abbreviated TDP, is a nucleotide. ... Deoxyguanosine diphosphate is a derivative of the common nucleic acid GTP, or guanosine triphosphate, in which the -OH (hydroxyl) group on the 2 carbon on the nucleotides pentose has been removed (hence the deoxy- part of the name). ... Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ... Deoxy adenosine triphosphate produces energy within the cells and is the basis for normal functioning of all body systems and organs. ... 3D-Model of thymidine triphosphate Thymidine triphosphate or TTP is one of the four nucleoside triphosphates that make up DNA. It can be used by DNA ligase to create overlapping sticky ends so that protruding ends of opened microbial plasmids maybe closed up. ... The chemical structure of dGTP Deoxyguanosine triphosphate, normally shortened to dGTP has a chemical structure of Na4 â€¢ 3 H2O and a molecular weight of 649. ... This article or section is in need of attention from an expert on the subject. ... Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions... Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions... The life cycle of an mRNA in a eukaryotic cell. ... Piwi-interacting RNA (piRNA) is a class of small RNA molecules that is expressed uniquely in mammalian testes and forms RNA-protein complexes with Piwi proteins. ... It has been suggested that Queuine be merged into this article or section. ... Ribosomal RNA (rRNA), a type of RNA synthesized in the nucleolus by RNA Pol I, is the central component of the ribosome, the protein manufacturing machinery of all living cells. ... A non-coding RNA (ncRNA) is any RNA molecule that is not translated into a protein. ... Guide RNA (gRNA) is a type of RNA that is used in mRNA editing. ... A short hairpin RNA (shRNA) is a sequence of RNA that makes a tight hairpin turn that can be used in gene expression silence. ... Mediating RNA interference in cultured mammalian cells. ... A non-coding RNA (ncRNA) is any RNA molecule that functions without being translated into a protein. ... The stem-loop secondary structure of a pre-microRNA from Brassica oleracea. ... A non-coding RNA (ncRNA) is any RNA molecule that functions without being translated into a protein. ... Mitochondrial DNA (some captions in German) Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria. ... In genetics, complementary DNA (cDNA) is DNA synthesized from a mature mRNA template. ... Figure 1: Schematic drawing of a bacterium with plasmids enclosed. ... A cosmid is a type of plasmid (often used as a cloning vector) constructed by the insertion of cos sequences, DNA-Sequences of the Phage Lambda Virus. ... A bacterial artificial chromosome (BAC) is a DNA construct, based on a fertility plasmid (or F-plasmid), used for transforming and cloning in bacteria, usually E. coli. ... A yeast artificial chromosome (short YAC) is a vector used to clone large DNA fragments (larger than 100 kb and up to 3000 kb). ... A human artificial chromosome (short HAC) is a microchromosome that can act as a new chromosome in a population of human cells. ... Look up nucleic acid in Wiktionary, the free dictionary. ... Glycerol nucleic acid (GNA) is a chemical similar to DNA or RNA but differing in the composition of its backbone. GNA is not known to occur naturally in existing life on Earth. ... PNA can also refer to the Palestinian National Authority or Pakistan National Alliance. ... TNA is threose nucleic acid, a chemical similar to DNA or RNA but differing in the composition of its backbone. ... Segment of a Morpholino-RNA heteroduplex, 8-mer shown In molecular biology, a Morpholino is a kind of molecule used to modify gene expression. ... A locked nucleic acid (LNA) is a modified RNA nucleotide. ...


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