Saturday, 25 January 2014

Where does New Genes Come from?

Researchers at the University of California, Davis, have now answered the most long standing question of origin of new genes. It is Non- coding DNA that rapidly turns into new genes!

"This shows very clearly that genes are being born from ancestral sequences all the time," said David Begun, professor of evolution and ecology at UC Davis and senior author on the paper.

A model proposed by Nobel laureate Susumu Ohno shows that when already present genes duplicate and diverge in functions, new functions seem to appear in genes. In past few years, it has also been noted in many different animals and plants that new genes can also appear from non- coding previously existing DNA sequences. According to Li Zhao, a postdoctoral researcher at UC Davis and first author on the paper, this is the first example of totally new genes still spreading through a species. She looked at RNA transcripts that corresponds to expressed genes , in the testes of several wild-derived strains of the fruit fly Drosophila melanogaster, and compared them to transcripts expressed in the standard reference sequence strain and in two closely related species. What she found was amazing!
248 new genes that exist only in D. melanogaster were discovered. Just over a hundred of which were "fixed," or already spread throughout the population. These genes were the result of ancestrally non-coding DNA since D. melanogaster split from its close relative, D. simulans. They fell into two wide classes: genes that were found at high frequency, meaning that they were spreading through the population as flies carrying them gained an edge in reproduction. These tended to be larger and more complex, and therefore likely had more significant functions, than those found at low frequency. Possibly these new genes form when a random mutation in the regulatory machinery causes a piece of non-coding DNA to be transcribed to RNA.
Initially researchers studied testis because of relatively high rate of adaptive evolution for male reproductive function. However, They plan to expand their studies to other tissues.