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Encyclopedia > Transcription (genetics)
A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. "Begin" indicates the 5' end of the DNA, where new RNA synthesis begins; "end" indicates the 3' end, where the primary transcripts are almost complete.
A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. "Begin" indicates the 5' end of the DNA, where new RNA synthesis begins; "end" indicates the 3' end, where the primary transcripts are almost complete.

Transcription is the process through which a DNA sequence is enzymatically copied by an RNA polymerase to produce a complementary RNA. In other words, it is the transfer of genetic information from DNA into RNA. In the case of protein-encoding DNA, transcription is the beginning of the process that ultimately leads to the translation of the genetic code (via the mRNA intermediate) into a functional peptide or protein. The stretch of DNA that is transcribed into an RNA molecule is called a transcription unit. Transcription has some proofreading mechanisms, but they are fewer and less effective than the controls for copying DNA; therefore, transcription has a lower copying fidelity than DNA replication.[citation needed] Image File history File links Download high-resolution version (1039x1250, 533 KB) Micrograph of gene transcription in progress, original author identified as Dr. Hans-Heinrich Trepte. ... Image File history File links Download high-resolution version (1039x1250, 533 KB) Micrograph of gene transcription in progress, original author identified as Dr. Hans-Heinrich Trepte. ... A non-coding RNA (ncRNA) is any RNA molecule that functions without being translated into a protein. ... Primary transcript is an RNA molecule that has not yet undergone any modification after its synthesis. ... In molecular biology, the 5 end and the 3 end (pronounced 5-prime and 3-prime) are respectively the leading and tail ends of a strand of nucleic acid. ... In molecular biology, the 5 end and the 3 end (pronounced 5-prime and 3-prime) are respectively the leading and tail ends of a strand of nucleic acid. ... The structure of part of a DNA double helix Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions for the development and function of living organisms. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... RNAP from pictured during elongation. ... Ribonucleic acid (RNA) is a nucleic acid polymer consisting of nucleotide monomers, that acts as a messenger between DNA and ribosomes, and that is also responsible for making proteins out of amino acids. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... The interaction of mRNA in a eukaryote cell. ... 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. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... It has been suggested that DNA replicate, Replisome, Replication fork, Lagging strand, Leading strand be merged into this article or section. ...


As in DNA replication, transcription proceeds in the 5' → 3' direction (i.e. the old polymer is read in the 3' → 5' direction and the new, complementary fragments are generated in the 5' → 3' direction). Transcription is divided into 3 stages: initiation, elongation and termination. It has been suggested that DNA replicate, Replisome, Replication fork, Lagging strand, Leading strand be merged into this article or section. ...

Contents

Initiation in prokaryotes

Transcription of RNA differs from DNA synthesis in that only one strand of DNA, the template strand, is used to make mRNA. Because transcription only proceeds in the 5' → 3' direction, it follows that the DNA template strand that is used must be oriented in 3' → 5' (complementary) direction. The strand that is not used as a template strand is called the non-template strand. Thus, DNA exists as a double strand, whereas RNA only exists as a single strand. The difference is due to the fact that DNA replication is semi-conservative, while transcription results in de novo production of a single strand of RNA. A summary of the three postulated methods of DNA synthesis Semiconservative replication describes the method by which DNA is replicated in all known cells. ... In general usage, de novo is a Latin expression meaning afresh, anew, beginning again. In Banking, a de novo bank is defined as a state member bank that has been in operation for five years or less. ...


Transcription begins with the binding of RNA polymerase to the promoter in DNA. The RNA polymerase is a core enzyme consisting of five subunits: 2 α subunits, 1 β subunit, 1 β' subunit, and 1 ω subunit. At the start of initiation, the core enzyme is associated with a sigma factor (number 70) that aids in finding the appropriate -35 and -10 basepairs downstream of promoter sequences. Unlike DNA replication, transcription does not need a primer to start. The DNA unwinds and produces a small open complex and synthesis begins on only the template strand. RNAP from pictured during elongation. ... 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. ... Downstream refers to a relative position in DNA or RNA. Each strand of DNA or RNA has a 5 end and a 3 end, so named for the carbons on the deoxyribose ring. ... It has been suggested that DNA replicate, Replisome, Replication fork, Lagging strand, Leading strand be merged into this article or section. ... A primer is a nucleic acid strand, or a related molecule that serves as a starting point for DNA replication. ...


Elongation

Unlike DNA replication, mRNA transcription can involve multiple RNA polymerases, so many mRNA molecules can be produced from a single copy of the gene. This step also involves a proofreading mechanism that can replace an incorrectly added RNA molecule.


Termination

Upon seeing a termination codon within the DNA template, RNA transcription can stop by forming a secondary hairpin loop that lets it come off the DNA template. Alternatively, another protein designated "Rho" can pull the mRNA away from polymerase.[citation needed] Hairpin structure of RNA A hairpin loop in RNA is a sequence of nucleotides where a long segment of RNA can base-pair with each other, but a segment within that sequence can not base pair, causing a hairpin loop. ...


Prokaryotic vs. eukaryotic transcription

Prokaryotic transcription occurs in the cytoplasm alongside translation. ... It has been suggested that Cytoplast be merged into this article or section. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... Eukaryotic transcription is more complex than Prokaryotic transcription, because eukaryotes have evolved much more complex transcriptional regulatory mechanisms than prokaryotes. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... It has been suggested that Cytoplast be merged into this article or section. ...

Measuring and detecting transcription

Transcription can be measured and detected in a variety of ways:

The northern blot is a technique used in molecular biology research to study gene expression. ... RT-PCR (Reverse Transcription-PCR) is a modification of PCR in which an RNA strand is first reverse transcribed into its DNA complement or cDNA, followed by amplification of the resulting DNA using PCR. This can either be a 1 or 2 step process. ... In situ hybridization (ISH) is a type of hybridization that uses a labeled complementary DNA or RNA strand (i. ... A DNA microarray (also DNA chip or gene chip in common speech) is a piece of glass or plastic on which pieces of DNA have been affixed in a microscopic array. ...

Transcription factories

Active transcription units are clustered in the nucleus, in discrete sites called ‘transcription factories’. Such sites could be visualized after allowing engaged polymerases to extend their transcripts in tagged precursors (Br-UTP or Br-U), and immuno-labeling the tagged nascent RNA. Transcription factories can also be localized using fluorescence in situ hybridization, or marked by antibodies directed against polymerases. There are ~10,000 factories in the nucleoplasm of a HeLa cell, among which are ~8,000 polymerase II factories and ~2,000 polymerase III factories. Each polymerase II factory contains ~8 polymerases. As most active transcription units are associated with only one polymerase, each factory will be associated with ~8 different transcription units. These units might be associated through promoters and/or enhancers, with loops forming a ‘cloud’ around the factory. Hela is also the German name for Hel, Poland and the cruiser SMS Hela In biological and medical research, a HeLa cell is a cell which is derived from cervical cancer cells taken from a woman named Henrietta Lacks, who died from the cancer in 1951, and circulated (without Lacks...


Transcription initiation complex

Transcription factors mediate the binding of RNA polymerase and the initiation of transcription. The RNA polymerase only binds to the promoter after certain transcription factors are assembled. The completed assembly of transcription factors and RNA polymerase bound to the promoter is called the transcription initiation complex. In the context of genetics, a transcription factor is a regulatory protein that initiates the transcription of certain genes upon binding with DNA. The binding of a transcription factor to a specific DNA sequence can result in either an increased rate of transcription of the gene, known as activated transcription...


History

A molecule which allows the genetic material to be realized as a protein was first hypothesized by Jacob and Monod. RNA synthesis by RNA polymerase was established in vitro by several laboratories by 1965; however, the RNA synthesized by these enzymes had properties that suggested the existence of an additional factor needed to terminate transcription correctly. François may refer to: a French name - Francis in English François is part of the name of several communes in France: François, in the Deux-Sèvres département Saint-François-de-Sales, in the Savoie département Saint-François-Lacroix, in the Moselle d... Jacques Lucien Monod (February 9, 1910 – May 31, 1976) was a French biologist and a Nobel Prize Winner in Physiology or Medicine in 1965. ... RNAP from pictured during elongation. ... Wiktionary has a definition of: In vitro In vitro (Latin: within glass) means within a test tube, or, more generally, outside a living organism or cell. ...


Recently, Roger D. Kornberg won the 2006 Nobel Prize in Chemistry "for his studies of the molecular basis of eukaryotic transcription".[1] Roger D. Kornberg two days after his Nobel Prize was declared, at the felicitation at Stanford University held at Fairchild audotorium, in the same building complex where he works. ... This is a list of Nobel Prize laureates in Chemistry from 1901 to 2006. ...


Terminology

  • Activator, is a DNA-binding protein that regulates one or more genes by increasing the rate of transcription.
  • Repressor, is a DNA-binding protein that regulates one or more genes by decreasing the rate of transcription.
  • Upstream, denotes the region to the left of the +1 (or towards the 5' end) transcription initiation site.
  • Downstream, denotes the region to the right (or towards the 3') of the termination site.
  • Thus, transcription of a single gene follows this pattern:

5'- promoter - +1 transcription initiation site - RNA-coding sequence - terminator - transcription termination site - 3' DNA-binding proteins are a broad class of protein molecules that possess certain structural motifs (e. ... For a non-technical introduction to the topic, see Introduction to Genetics. ...


<-- upstream downstream -->


Reverse transcription

Scheme of reverse transcription

Some viruses (such as HIV, the cause of AIDS), have the ability to transcribe RNA into DNA in order to see a cell's genome. The main enzyme responsible for this type of transcription is called reverse transcriptase. In the case of HIV, reverse transcriptase is responsible for synthesising a complementary DNA strand (cDNA) to the viral RNA genome. An associated enzyme, ribonuclease H, digests the RNA strand and reverse transcriptase synthesises a complementary strand of DNA to form a double helix DNA structure. This cDNA is integrated into the host cell's genome via another enzyme (integrase) causing the host cell to generate viral proteins which reassemble into new viral particles. Subsequently, the host cell undergoes programmed cell death (apoptosis). Image File history File links RetroTranscription. ... Image File history File links RetroTranscription. ... Species Human immunodeficiency virus 1 Human immunodeficiency virus 2 Human immunodeficiency virus (HIV) is a retrovirus that causes acquired immunodeficiency syndrome (AIDS, a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections). ... Acquired Immune Deficiency Syndrome or acquired immunodeficiency syndrome (AIDS or Aids) is a collection of symptoms and infections resulting from the specific damage to the immune system caused by the human immunodeficiency virus (HIV). ... 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. ... In genetics, complementary DNA (cDNA) is DNA synthesized from a mature mRNA template. ...


References

  1. ^ Chemistry 2006. Nobel Foundation. Retrieved on 2007-03-29.

2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the CE era. ... March 29 is the 88th day of the year in the Gregorian calendar (89th in leap years). ...

See also

For a non-technical introduction to the topic, please see Introduction to genetics. ... Molecular biology is the study of biology at a molecular level. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. ... In genetics, splicing is a modification of genetic information after transcription, in which introns are removed and exons are joined. ... 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... ... Bookmarking is a biological phenomenon believed to function as an epigenetic mechanism for transmitting cellular memory of the pattern of gene expression in a cell through mitosis to its daughter cells. ...

Further reading

  • Lehninger Principles of Biochemistry, 4th edition, David L. Nelson & Michael M. Cox
  • Principles of Nuclear Structure and Function, Peter R. Cook
  • Essential Genetics, Peter J. Russell

External links

Wikiversity
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Transcription (genetics)

  Results from FactBites:
 
Botany online: Molecular Genetics - Transcription (2301 words)
Transcription is the process during which the genetic information is transcribed from DNA into RNA.
Transcription is similar to DNA replication in that one of the two DNA strands acts as a template on which the base-pairing abilities of the incoming RNA nucleotide are tested.
Transcription is finished as soon as the polymerase reaches a termination sequence.
  More results at FactBites »

 
 

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