Evolution of new genes captured
Like job-seekers searching for a new position, living things sometimes have to pick up a new skill if they are going to succeed. Researchers from the University of California, Davis, and Uppsala University, Sweden, have shown for the first time how living organisms do this.
The observation, published Oct. 19 in the journal Science, closes an important gap in the theory of natural selection.
Scientists have long wondered how living things evolve new functions from a limited set of genes. One popular explanation is that genes duplicate by accident; the duplicate undergoes mutations and picks up a new function; and, if that new function is useful, the gene spreads.
"It’s an old idea and it’s clear that this happens," said John Roth, a distinguished professor of microbiology at UC Davis and co-author of the paper.
The problem, Roth said, is that it has been hard to imagine how it occurs. Natural selection is relentlessly efficient in removing mutated genes: Genes that are not positively selected are quickly lost.
How then does a newly duplicated gene stick around long enough to pick up a useful new function that would be a target for positive selection?
Experiments in Roth’s laboratory and elsewhere led to a model for the origin of a novel gene by a process of “innovation, amplification and divergence.” This model has now been tested by Joakim Nasvall, Lei Sun and Dan Andersson at Uppsala.
