FACTOID # 29: 73.3% of America's gross operating surplus in motion picture and sound recording industries comes from California.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Gene expression

Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. For a non-technical introduction to the topic, see Introduction to Genetics. ... 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... A gene product is the biochemical material, either RNA or protein, resulting from expression of a gene. ... 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...


Several steps in the gene expression process may be modulated, including the transcription step and the post-translational modification of a protein. Gene regulation gives the cell control over structure and function, and is the basis for cellular differentiation, morphogenesis and the versatility and adaptability of any organism. Gene regulation may also serve as a substrate for evolutionary change, since control of the timing, location, and amount of gene expression can have a profound effect on the functions (actions) the gene in the organism. A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... Posttranslational modification means the chemical modification of a protein after its translation. ... Embryonic stem cells differentiate into cells in various body organs. ... Morphogenesis (from the Greek morphê shape and genesis creation) is one of three fundamental aspects of developmental biology along with the control of cell growth and cellular differentiation. ... “Life on Earth” redirects here. ...


Non-protein coding genes (e.g. rRNA genes, tRNA genes) are not translated into protein. A non-coding RNA (ncRNA) is any RNA molecule that functions without being translated into a protein. ... Transfer RNA (abbreviated tRNA) is a small RNA chain (74-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ...

Contents

Measurement

The expression of many genes is regulated after transcription (i.e., by microRNAs or ubiquitin ligases), so an increase in mRNA concentration need not always increase expression. Nevertheless, mRNA levels can be quantitatively measured by Northern blotting, a process in which a sample of RNA is separated on an agarose gel and hybridized to a radio-labeled RNA probe that is complementary to the target sequence. Northern blotting requires the use of radioactive reagents and can have lower data quality than more modern methods (due to the fact that quantification is done by measuring band strength in an image of a gel), but it is still often used. It does, for example, offer the benefit of allowing the discrimination of alternately spliced transcripts. The stem-loop secondary structure of a pre-microRNA from Brassica oleracea. ... A Ubiquitin ligase is a protein which covalently attaches ubiquitin to a lysine residue on a target protein. ... The Northern Blot is a technique used in molecular biology research to study gene expression. ... A polysaccharide obtained from agar that is the most widely used medium for gel electrophoresis procedures. ...


A more modern low-throughput approach for measuring mRNA abundance is real-time polymerase chain reaction or RT-PCR. With a carefully constructed standard curve RT-PCR can produce an absolute measurement such as number of copies of mRNA per nanolitre of homogenized tissue. The lower level of noise in data obtained via RT-PCR often makes this the method of choice, but the price of the required equipment and reagents can be prohibitive. In molecular biology, real-time polymerase chain reaction, also called quantitative real time polymerase chain reaction (QRT-PCR) or kinetic polymerase chain reaction, is a laboratory technique used to simultaneously quantify and amplify a specific part of a given DNA molecule. ...


In addition to low-throughput methods, transcript levels for many genes at once can be measured with DNA microarray technology or "tag based" technologies like Serial analysis of gene expression (SAGE) or the more advanced version SuperSAGE, which can provide a relative measure of the cellular concentration of different messenger RNAs. Recent advances in microarray technology allow for the quantification, on a single array, of transcript levels for every known gene in the human genome. The great advantage of tag-base methods is the "open architechture", allowing for the exact measuremnet of any transcript, known or unknown. Especially SuperSAGE recommends itself therefore also for studying organisms with unknown genomes. It has been suggested that Gene chip technology be merged into this article or section. ... Serial analysis of gene expression (SAGE) is a technique used by molecular biologists to produce a snapshot of the messenger RNA population in a sample of interest. ... In chemistry, concentration is the measure of how much of a given substance there is mixed with another substance. ... The life cycle of an mRNA in a eukaryotic cell. ...


Protein levels themselves can be estimated by a number of means. The most commonly used method is to perform a Western blot against the protein of interest, whereby cellular lysate is separated on a polyacrylamide gel and then probed with an antibody to the protein of interest. The antibody can either be conjugated to a fluorophore or to horseradish peroxidase for imaging or quantification. Another commonly used method for assaying the amount of a particular protein in a cell is to fuse a copy of the protein to a reporter gene such as Green fluorescent protein, which can be directly imaged using a fluorescent microscope. Because it is very difficult to clone a GFP-fused protein into its native location in the genome, however, this method often cannot be used to measure endogenous regulatory mechanisms (GFP-fusions are therefore most often expressed on extra-genomic DNA such as an expression vector). Fusing a target protein to a reporter can also change the protein's behavior, including its cellular localization and expression level. Figure 1. ... ... // A polyacrylamide gel is a separation matrix used in electrophoresis of biomolecules, such as proteins or DNA fragments. ... A fluorophore is a component of a molecule which causes a molecule to be fluorescent. ... The enzyme horseradish peroxidase, found in horseradish, is used extensively in molecular biology in antibody amplification and detection, among other things[1]. For example, In recent years the technique of marking neurons with the enzyme horseradish peroxidase (HRP) has become a major tool. ... It has been suggested that mGFP be merged into this article or section. ... This article or section does not cite its references or sources. ...


The pattern of detection of a gene or gene product may be described using terms such as facultative, constitutive, circadian, cyclic, housekeeping, or inducible [1].


Regulation of gene expression

Regulation of gene expression is the cellular control of the amount and timing of appearance of the functional product of a gene. Any step of gene expression may be modulated, from the DNA-RNA transcription step to post-translational modification of a protein. Gene regulation gives the cell control over structure and function, and is the basis for cellular differentiation, morphogenesis and the versatility and adaptability of any organism. Gene modulation redirects here. ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... Posttranslational modification means the chemical modification of a protein after its translation. ... Embryonic stem cells differentiate into cells in various body organs. ... Morphogenesis (from the Greek morphê shape and genesis creation) is one of three fundamental aspects of developmental biology along with the control of cell growth and cellular differentiation. ... “Life on Earth” redirects here. ...


Expression system

An expression system consists, minimally, of a source of DNA and the molecular machinery required to transcribe the DNA into mRNA and translate the mRNA into protein using the nutrients and fuel provided. In the broadest sense, this includes every living cell capable of producing protein from DNA. However, an expression system more specifically refers to a laboratory tool, often artificial in some manner, used for assembling the product of a specific gene or genes. It is defined as the "combination of an expression vector, its cloned DNA, and the host for the vector that provide a context to allow foreign gene function in a host cell, that is, produce proteins at a high level" [2][3]. 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. ... Molecular systems that are able to shift a chemical or mechanical process away from equilibrium represent a potentially important branch of chemistry and nanotechnology. ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... The interaction of mRNA in a eukaryote cell. ... Translation is an activity comprising the interpretation of the meaning of a text in one language—the source text—and the production of a new, equivalent text in another language—the target text, also called the translation. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Look up artificial in Wiktionary, the free dictionary. ... This article or section does not cite its references or sources. ...


In addition to these biological tools, certain naturally observed configurations of DNA (genes, promoters, enhancers, repressors) and the associated machinery itself are referred to as an expression system, as in the simple repressor 'switch' expression system in Lambda phage. It is these natural expression systems that inspire artificial expression systems, (such as the Tet-on and Tet-off expression systems). Enterobacteria phage λ (lambda phage) is a temperate bacteriophage that infects Escherichia coli. ... Tetracycline Controlled Transcriptional Activation is a method of inducible expression where transcription is reversibly turned on or off in the presence of the antibiotic tetracycline or one of its derivatives (etc. ...


Each expression system has distinct advantages and liabilities, and may be named after the host, the DNA source or the delivery mechanism for the genetic material. For example, common expression systems include bacteria (such as E.coli), yeast (such as S.cerevisiae), plasmid, artificial chromosomes, phage (such as lambda), cell lines, or virus (such as baculovirus, retrovirus, adenovirus). 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. ... E. coli redirects here. ... Typical divisions Ascomycota (sac fungi) Saccharomycotina (true yeasts) Taphrinomycotina Schizosaccharomycetes (fission yeasts) Basidiomycota (club fungi) Urediniomycetes Sporidiales Yeasts are a growth form of eukaryotic microorganisms classified in the kingdom Fungi, with approximately 1,500 species described. ... Binomial name Saccharomyces cerevisiae Meyen ex E.C. Hansen Saccharomyces cerevisiae is a species of budding yeast. ... Figure 1: Schematic drawing of a bacterium with plasmids enclosed. ... Yeast artificial chromosome Bacterial artificial chromosome Human artificial chromosome Category: ... This article or section does not cite its references or sources. ... Enterobacteria phage λ (lambda phage) is a temperate bacteriophage that infects Escherichia coli. ... Epithelial cells in culture, stained for keratin (red) and DNA (green) Cell culture is the process by which either prokaryotic or eukaryotic cells are grown under controlled conditions. ... 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... The baculoviruses are a family of large rod-shaped viruses that can be divided to two genera: nucleopolyhedroviruses (NPV) and granuloviruses (GV). ... Genera Alpharetrovirus Betaretrovirus Gammaretrovirus Deltaretrovirus Epsilonretrovirus Lentivirus Spumavirus A retrovirus is any virus belonging to the viral family Retroviridae. ... Genera Mastadenovirus Aviadenovirus Atadenovirus Siadenovirus Adenoviruses are viruses of the family Adenoviridae. ...


Overexpression

In the laboratory, the protein encoded by a gene is sometimes expressed in increased quantity. This can come about by increasing the number of copies of the gene or increasing the binding strength of the promoter region.


Often, the DNA sequence for a protein of interest will be cloned or subcloned into a plasmid containing the lac promoter, which is then transformed into the bacterium Escherichia coli. Addition of IPTG (a lactose analog) causes the bacteria to express the protein of interest. However, this strategy does not always yield functional protein, in which case, other organisms or tissue cultures may be more effective. As for example the yeast, Saccharomyces cerevisiae, is often preferred to bacteria for proteins that undergo extensive Posttranslational modification. Nonetheless, bacterial expression has the advantage of easily producing large amounts of protein, which is required for X-ray crystallography or nuclear magnetic resonance experiments for structure determination. For other uses, see clone. ... In molecular biology, subcloning is a technique used to move a particular gene of interest from a parent vector to a destination vector in order to further study its functionality. ... Figure 1: Schematic drawing of a bacterium with plasmids enclosed. ... The lac operon is an operon required for the transport and metabolism of lactose in Escherichia coli and some other enteric bacteria. ... It has been suggested that this article or section be merged into Transfection. ... E. coli redirects here. ... IPTG is a common abbreviation for Isopropyl β-D-1-thiogalactopyranoside, a molecular biology reagent. ... Lactose is a disaccharide that consists of β-D-galactose and β-D-glucose molecules bonded through a β1-4 glycosidic linkage. ... “Life on Earth” redirects here. ... Tissue culture refers to the growth of tissues and/or cells separate from the organism. ... Typical divisions Ascomycota (sac fungi) Saccharomycotina (true yeasts) Taphrinomycotina Schizosaccharomycetes (fission yeasts) Basidiomycota (club fungi) Urediniomycetes Sporidiales Yeasts are a growth form of eukaryotic microorganisms classified in the kingdom Fungi, with approximately 1,500 species described. ... Binomial name Saccharomyces cerevisiae Meyen ex E.C. Hansen Saccharomyces cerevisiae is a species of budding yeast. ... Posttranslational modification is the chemical modification of a protein after its translation. ... X-ray crystallography, also known as single-crystal X-ray diffraction, is the oldest and most common crystallographic method for determining the structure of molecules. ... Pacific Northwest National Laboratorys high magnetic field (800 MHz, 18. ...


Gene networks and expression

Genes have sometimes been regarded as nodes in a network, with inputs being proteins such as transcription factors, and outputs being the level of gene expression. The node itself performs a function, and the operation of these functions have been interpreted as performing a kind of information processing within cell and determine cellular behaviour. A gene regulatory network (also called a GRN or genetic regulatory network) is a collection of DNA segments in a cell which interact with each other (indirectly through their RNA and protein expression products) and with other substances in the cell, thereby governing the rates at which genes in the... 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. ... In general, information processing is the changing (processing) of information in any manner detectable by an observer. ...


Techniques

  • Primer: Used to facilitate expression
  • Shuttle Vector

See also

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. ... Expression Profiling Microarray technology is often used for expression profiling. ... An expressed sequence tag or EST is a short sub-sequence of a transcribed spliced nucleotide sequence (either protein-coding or not). ... Paramutation, in genetics, is an interaction between two alleles of a single locus, resulting in a heritable change of one allele. ... Sequence profiling Tools in bioinformatics refer to all those software tools (web-based/downloadable) that provide a brief overview on all related information about an input sequence. ... A genetically modified organism (GMO) is an organism whose genetic material has been altered using the genetic engineering techniques generally known as recombinant DNA technology. ... 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. ...

References

  1. ^ Glossary of gene expression terms
  2. ^ cancerweb definition definition of expression system
  3. ^ biology-online.org definition of expression system

See also: gene expression, List of Glossaries, List of Natural Sciences Glossaries A constitutive gene or constitutive expression describes a gene that is transcribed continually compared to a facultative gene which is only transcribed when needed. ...

External links


  Results from FactBites:
 
Cell-Specific Gene Expression (1046 words)
For example, expression of the insulin gene in the beta cells of the islets of Langerhans can be monitored by measuring the level of insulin in the blood.
With gene splicing, the promoter of a gene whose expression you wish to monitor can be coupled to the coding sequence of a chosen "reporter" gene.
This is done by fusing the gene for GFP to the gene whose expression you are interested in.
Gene expression - Wikipedia, the free encyclopedia (736 words)
Gene expression, or simply expression, is the process by which a gene's DNA sequence is converted into the structures and functions of a cell.
An inducible gene is a gene whose expression is either responsive to environmental change or dependent on the position of the cell cycle.
Genes have sometimes been regarded as nodes in a network, with inputs being proteins such as transcription factors, and outputs being the level of gene expression.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m