Changing concept of Gene
The concept of the Gene has changed considerably (see history section). From the original definition of a "unit of inheritance", the term evolved to mean a [DNA]Create?-based unit that can exert its effects on the organism through RNA or protein products. It was also previously believed that one Gene makes one protein; this concept was overthrown by the discovery of alternative splicing and trans-splicing.
The definition of a Gene is still changing. The first cases of RNA-based inheritance have been discovered in mammals. (Rassoulzadegan and colleagues (2006) RNA-mediated non-Mendelian inheritance of an epigenetic change in the mouse. PMID 16724059) Evidence is also accumulating that the control regions of a Gene do not necessarily have to be close to the coding sequence on the linear [molecule]Create? or even on the same [chromosome]Create?. Spilianakis and colleagues discovered that the promoter region of the interferon-gamma gene on [chromosome]Create? 10 and the regulatory regions of the T(H)2 cytokine locus on [chromosome]Create? 11 come into close proximity in the nucleus possibly to be jointly regulated. (Spilianakis & colleagues (2005) Interchromosomal associations between alternatively expressed loci. PMID 15880101)
The concept that genes are clearly delimited is also being eroded. There is evidence for fused proteins stemming from two adjacent genes that can produce two separate protein products. While it is not clear whether these fusion proteins are functional, the phenomena is more frequent than previously thought. (Parra & colleagues (2006) Tandem chimerism as a means to increase protein complexity in the [human genome]Create?. PMID 16344564) Even more ground-breaking than the discovery of fused genes is the observation that some proteins can be composed of exons from far away regions and even different chromosomes. (Kapranov & colleagues (2005) Examples of the complex architecture of the human transcriptome revealed by RACE and high-density tiling arrays. PMID 15998911) This new data has led to an updated, and probably tentative, definition of a gene as "a union of genomic sequences encoding a coherent set of potentially overlapping functional products." (
Mark B. Gerstein et al., "What is a Gene, post-ENCODE? History and updated definition," Genome Research 17(6) (2007): 669-681
) This new definition categorizes genes by functional products, whether they be proteins or RNA, rather than specific DNA loci; all regulatory elements of DNA are therefore classified as gene-associated regions.
See also:
Changing concept of gene
The concept of the Gene has changed considerably (see history section). From the original definition of a "unit of inheritance", the term evolved to mean a [DNA]Create?-based unit that can exert its effects on the organism through RNA or protein products. It was also previously believed that one Gene makes one protein; this concept was overthrown by the discovery of alternative splicing and trans-splicing.
The definition of a Gene is still changing. The first cases of RNA-based inheritance have been discovered in mammals. (Rassoulzadegan and colleagues (2006) RNA-mediated non-Mendelian inheritance of an epigenetic change in the mouse. PMID 16724059) Evidence is also accumulating that the control regions of a Gene do not necessarily have to be close to the coding sequence on the linear [molecule]Create? or even on the same [chromosome]Create?. Spilianakis and colleagues discovered that the promoter region of the interferon-gamma gene on [chromosome]Create? 10 and the regulatory regions of the T(H)2 cytokine locus on [chromosome]Create? 11 come into close proximity in the nucleus possibly to be jointly regulated. (Spilianakis & colleagues (2005) Interchromosomal associations between alternatively expressed loci. PMID 15880101)
The concept that genes are clearly delimited is also being eroded. There is evidence for fused proteins stemming from two adjacent genes that can produce two separate protein products. While it is not clear whether these fusion proteins are functional, the phenomena is more frequent than previously thought. (Parra & colleagues (2006) Tandem chimerism as a means to increase protein complexity in the [human genome]Create?. PMID 16344564) Even more ground-breaking than the discovery of fused genes is the observation that some proteins can be composed of exons from far away regions and even different chromosomes. (Kapranov & colleagues (2005) Examples of the complex architecture of the human transcriptome revealed by RACE and high-density tiling arrays. PMID 15998911) This new data has led to an updated, and probably tentative, definition of a gene as "a union of genomic sequences encoding a coherent set of potentially overlapping functional products." (
Mark B. Gerstein et al., "What is a Gene, post-ENCODE? History and updated definition," Genome Research 17(6) (2007): 669-681
) This new definition categorizes genes by functional products, whether they be proteins or RNA, rather than specific DNA loci; all regulatory elements of DNA are therefore classified as gene-associated regions.
See also:
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