Genes in tandem
Scientists have revealed the secret of twin genes
Geneticists from Stanford University have found out why some copies of genes that have been doubled as a result of mutations remain in the genome, despite the fact that most of them are lost or lose their functions. It turned out that the twin genes begin to support each other's work and the loss of one of them negatively affects the performance of the other. The study was published in the journal Science (Xun Lan, Jonathan K. Pritchard, Coregulation of tandem duplicate genes slows evolution of subfunctionalization in mammals; the full text of the author's version of the article can be read on the bioRxiv – VM website).
Duplication is the main source of genes with new functions. However, it is known that most copies, due to their redundancy, become easy targets for mutations that disrupt their work and turn them into pseudogenes. The half-life of duplicates is estimated at only four million years. However, some copies remain functional.
To understand what contributes to the preservation of duplicates, scientists examined the genomes of cells isolated from 46 types of human tissue and 26 types of mouse tissue. The researchers found that 15 percent of the doubled genes are preserved because they share the original function. This process is called subfunctionalization. One copy works in cells of one type of tissue, the second in cells of another type. The loss of one copy can negatively affect the vital activity of the organism, therefore it is not supported by selection.
However, most duplicates remain in the genome for other reasons. Subfunctionalization occurs over a long period of time, but genes compensate for their work much faster. After the appearance of a duplicate, the genes reduce their activity and act together. If a mutation occurs in one of them, then the other gene will not be enough to produce protein in normal quantities. Such mutations are also filtered out by selection.
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23.05.2016