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.
