A gene is a section on the Desoxyribonukleinsäure (DNA), which contains the basic informations for production of a biologically active Ribonukleinsäure (RNA). With this production process (Transkription called) a Negativkopie in form of the RNA is manufactured. It givesdifferent RNAs, which is most well-known mRNA, by which during the translation a protein is translated. This protein transfers a completely specific function, which can be called also characteristic in the body. Genes become general therefore as hereditary factor or Hereditary factor designates, since they are the carriers of heiress formation, which are passed on by reproduction to the descendants. The Expression, i.e. the development or the activity condition of a gene, are exactly adjusted in each cell.
The study of the structureand the function and transmission from genes is article of the genetics. The study of the whole of all genes of an organism ( the gene COM) is thing of the Genomik (English. genomics).
1854 began Gregor Mendel to examine the transmission of characteristics with peas. He suggested the existence of factors, which will transfer from parents to the descendants as the first. With its crossing attempts it described that characteristics can be left from each other independently,as well as dominant factor and rezessive characteristics. It developed the hypothesis the fact that there can be homo - and heterozygote conditions and put thereby the basis for the distinction between Genotyp and phenotype. The name “gene” became 1909 of the Dane William Johannsen coined/shaped. It designated the objects, with which the leaving teachings are occupied, after the Greek word genos (sex). Already three years before William Bateson the science of the transmission genetics had called, after the Greek word genetikos (bringing out).At this time the chemical nature of the genes was still perfectly unclear.
Thomas Hunt Morgan began 1910 with crossing attempts at blackbulgy baptizing couches. It could show as the first that genes lay on Chromosomen and later that it in certain placeson the Chromosomen lie. 1928 white Frederick Griffith in as “Griffiths the experiment “admit become attempt for the first time after that genes will transfer from organisms to others can. The procedure proven by it was the transformation.1941 showed George Wells Beadle and Edward Lawrie Tatum that mutations are responsible in genes for defects in metabolic pathways, which showed that specific genes code specific proteins. These realizations led to the “in gene in enzyme hypothesis “. Oswald Avery, Collin Macleod and Maclyn McCarty showed 1944 that the DNA contains the genetic information. 1953 became the structure of the DNA von James D. Watson and Francis Crick, based on the work of Rosalind Franklin, decodes. 1969 succeeded to Jonathan Beckwith asfirst the isolation of an individual gene.
on molecular level consists a gene of two different ranges:
- a DNA section, of by Transkription a einzelsträngige RNA copy all
- additional DNA sections, those is manufactured at the regularization of this copying processare involved.
There are different characteristics in the structure of genes of different organisms.
In the design the structure of a typical eukaryotischen gene is represented, which codes a protein. The transliterated gene part (prä mRNA) contains six ranges, those in this case Introns, those during the ripe process (processing) from the RNA to be removed and seven Exons, which link the ripe with one another mRNA form.
Before the Transkriptionseinheit or also within the Exons and Introns regulatorische elements lie howfor example Enhancer or activators. To these bind dependent on the sequence different proteins, as for example the Transkriptionsfaktoren and the RNA polymerase. Prä mRNA (does not mature mRNA), which in the cell core with the Transkription first develops, becomes during the maturing processto mature mRNA modified. mRNA contains apart from directly protein-coding open still untranslatierte, thus not-coding ranges, which 5 untranslatierten ' range (5 ' UTR) and the 3 ' untranslatierten range (3 ' UTR). These ranges serve for the regularization of the Translationsinitiation and forRegularization of the activity of the RNAsen, which diminish the RNA again.
the text the genes of the Prokaryoten in the structure from eukaryotischen genes by the fact that they do not possess Introns. Besides several different can RNA screen end of gene sections very near one behind the other switched its (one speaks then of polycistronischen genes) and in their activity from a common regulatorischen element to be regulated. This gene cluster are transliterated together, but translatiert into different proteins. This unit from regularization element and polycistronischenGenes calls one Operon. Operons are typical for Prokaryoten.
Genes code not only mRNA, from which the proteins are then translatiert , but also rRNA and tRNA as well as further Ribonukleinsäuren, the other tasks inthe cell have, for example with the protein biosynthesis or the gene regularization. A gene, which codes a protein, contains a description of the amino acid - sequence of this protein. This description is present in a chemical language, i.e. in the genetic code in form that Nucleotide - sequence of the DNA. The individual “track links” (nucleotides) the DNA represent - in tripartite groups (triplet) in summary - the “letters” of the genetic code. The coding range, thus all nucleotides, which are involved directly in the description of the amino acid sequence,open one calls. A nucleotide consists of a part phosphate, a part Desoxyribose (sugar) and a cousin. A cousin is either adenine, thymine, guanine or cytosine.
Genes can mutate, itself thus spontaneously or by effectchange from the outside (for example by radioactivity). These changes can take place in different places in the gene. Therefore a gene can be present after a set of mutations in different condition forms, which one calls alleles. A DNA sequence knows also several overlapping genescontained. By Genduplikation doubled genes can sequence-identically, although however differently adjusted its and thus to different amino acid sequences lead, would be thus no alleles.
gene activity and regularization
of genes are then “actively”, if their information in RNA is rewritten, i.e.the Transkription takes place. Depending upon function of the gene develops thus mRNA, tRNA or rRNA. In the consequence thus, does not have however not compellingly, with mRNA from this activity also a protein can be translatiert. An overview of the proceduresoffer the articles Genexpression and protein biosynthesis.
The activity of individual genes is steered and controlled via a multiplicity of mechanisms. A way is the control over the rate of its Transkription in RNA. Another way is the dismantling mRNA,before it is translatiert for example over siRNA. The gene regularization takes place at short notice via connection and separation from proteins, Transkriptionsfaktoren so mentioned, to specific ranges of the DNA, the “regulatorischen elements in such a way specified”. This becomes long-term over Methylierung or “packing” ofDNA sections in Histonkomplexe reaches. Also the regulatorischen elements of the DNA are subject to the variation. The influence of changes in the gene regularization including the controlling of the alternative Splicings might be comparable with the influence of mutations of protein-coding sequences. With classical genetic methods- by analysis of hereditary courses and phenotypes - these effects are to be separated in the transmission normally not. Only molecular biology can give references here. An overview of the regularization procedures of genes is represented in the article gene regularization.
Organization coded by
genes with all organisms only one part of the DNA for defined RNAs. The remaining parts of the DNA are called Nichtkodierende DNA. It has functions in the gene regularization, for example for the regularization of the alternative Splicings) and influence on the architecture of the Chromosomen has.
The place on a Chromosom, at which the gene is, is called gene place. Genes are in addition not even distributed on the Chromosomen, but come partially into so mentionedClustern forwards. Gene cluster can thereby of coincidental in spatial proximity to each other lying genes exist, or this concerns groups of genes, which code for proteins, which stand in a functional connection. Genes, whose proteins have similar function, can howeveralso on different Chromosomen lie.
Likewise, as there is not-coding DNA, there are sections on the DNA, which code for several different proteins. Basis for it are overlapping, from each other deviating so-called reader aster of the RNA polymerase.
genetic variation and geneticVariability
genetic variation is called the occurrence of genetic variants (alleles, genes or Genotypen) with individual organisms. It results by mutations, in addition, from procedures with the Meiose, from the hereditary factors of grandparents differently on those Sex cells to be distributed.
Genetic variability is against it the ability of an entire population to bring individuals out with different hereditary property. Here genetic procedures, but also mechanisms of the partner choice do not only play a role. The genetic variability plays a crucial role for thoseAbility of a population to survive under changed environmental condition and represents an important factor of the evolution .
of RNA genes in viruses
although with all cellbased ways of life of genes as DNA sections are present, give it some viruses, whose is present genetic information in the form of RNA. RNA viruses strike a cell, which begins then immediately with the production of proteins directly after guidance of the RNA; a Transkription from DNA to RNA is void.Retroviren however translate their RNAthe infection in DNA, under co-operation of the enzyme Reverse Transkriptase.
as gene strictly speaking one usually designates a nucleotide sequence, which contains the information for a protein, which is directly functional. Pseudo genes represent against it gene copies, which do not code functional protein in full length. Oftmals sind diese durch Genduplikationen entstanden und/oder durch Mutationen, welche sich in der Folge ohne Selektion auch im Pseudogenakkumulieren (anhäufen), und ihre ursprüngliche Funktion verloren haben.Some seem to play nevertheless a role with the adjustment of the gene activity. The human Genom contains about 20,000 pseudo genes.
you are designated also as Transposons and are mobile hereditary property goods, itself within the DNA the oneCell freely to move know. Of their traditional place in the hereditary property they cut out and add themselves in any different place. Biologists around Fred fee of the Salk of institutes in La Jolla (the USA) proved that thesejumping genes like so far accepted in the cells of the germ course do not only occur, but also in nerve forerunner cells are active.
typical Genomgrössen and number of genes
|of organisms or other biological systems||number of genes||of pairs of cousins|
|Mycoplasma genitalium||500||10 6|
- Ernst P. Fischer. History of theGene. 1. Edition, Fischer (Tb.), Frankfurt 2003, ISBN 3596153638
- Jaroslav Krizenecky: Gregor Johann Mendel, 1822-1884; Texts and sources to its working and living. In: Life representations of German natural scientists 11, Barth, Leipzig 1965
- Benjamin Lewin: (2002) Molecular biology of the genes. ISBN 3827413494
- of gene. ISBN 0131439812 (English)
- Inge crowning mountain: Which genes make humans humans? In: Biology in our time 34 (4), S. to 206 - 207 (2004), ISSN 0045-205X
|Wiktionary: Towards - word origin, synonyms and translations|
Web on the left of
- the long way to the gene: Milestones
- entry (English) in the Stanford Encyclopedia OF Philosophy (inclusive Literature data)
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