NationMaster - Encyclopedia: Transvection (genetics)

Transvection, in genetics, is a process in which the gene regulatory sequence of one allele on a chromosome interact with the coding sequence of the allele on the homologous chromosome. An allele with a mutation in the coding sequence, for example, can be complemented in trans by an allele with a mutation in a regulatory sequence through transvection. The result of transvection is a partial rescue of the wild type phenotype, even when the organism is heterozygous for two defective (mutant) alleles. Normally, an organism heterozygous for two defective alleles would have a mutant phenotype (non-complementation). Genetics (from the Greek genno Î³ÎµÎ½Î½ÏŽ= give birth) is the science of genes, heredity, and the variation of organisms. ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... A regulatory sequence is a promoter, enhancer or other segment of DNA where regulatory proteins such as transcription factors bind preferentially. ... An allele is any one of a number of viable DNA codings of the same gene (sometimes the term refers to a non-gene sequence) occupying a given locus (position) on a chromosome. ... Figure 1: Chromosome. ... Mutations are permanent, sometimes transmissible (if the change is to a germ cell) changes to the genetic material (usually DNA or RNA) of a cell. ... In biology, a wild type is one of the major genotypes of a species that occur in nature, in contrast to induced mutations or artificial cross-breeding. ... The phenotype of an individual organism is either its total physical appearance and constitution, or a specific manifestation of a trait, such as size or eye color, that varies between individuals. ...

Interestingly, transvection appears to be dependent upon somatic chromosome pairing. If one allele is placed on a different chromosome by a translocation (linking the allele to a different centromere), transvection does not occur. Transvection can be restored in a translocation homozygote, where both alleles are again linked to homologous centromeres. The centromere is a region of a eukaryotic chromosome where the kinetochore is assembled. ...

The mechanism of transvection is still unclear, yet it appears to be mediated by chromatin modifications facilitated by polycomb-like proteins (see epigenetics). Chromatin is the substance of a chromosome and consists of a complex of DNA and protein in eukaryotic cells. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... The term epigenetics has over time been used in various senses, in part because the Greek prefix epi- has at least six meanings in English (including on, after and in addition), but also because various theories of epigenetic development, inheritance, and evolution have been proposed (see Historical notes below). ...

Transvection has been observed only at a few loci in Drosophila. Species Many; see text. ...

Edward B. Lewis at Caltech discovered transvection at the bithorax complex in Drosophila in the 1950s. Edward B. Lewis (May 20, 1918â€“July 21, 2004) was an American geneticist, the winner of the 1995 Nobel Prize in Medicine. ... California Institute of Technology The California Institute of Technology (commonly known as Caltech) is a private, coeducational university located in Pasadena, California, in the United States. ... Species Many; see text. ... // Events and trends The 1950s in Western society was marked with a sharp rise in the economy for the first time in almost 30 years and return to the 1920s-type consumer society built on credit and boom-times, as well as the height of the baby-boom from returning...