So how does cryptic variation work and why is it so important for understanding evolution?
By allowing for a certain amount of mistakes to occur instead of quenching them with global proofreading machinery, organisms gain the advantage of allowing for what Masel calls pre-selection: It provides an opportunity for natural selection to act on sequences even before mutations occur.
"There is evidence that cryptic gene sequences still get translated into protein," Masel explained, "at least occasionally."
"When those proteins are bad enough, the sequences that produce them can be selected against. For example, if we imagine a protein with an altered amino acid sequence causing it to not fold correctly and pile up inside the cell, that would be very toxic to the organism."
"In this case of a misfolded protein, selection would favor mutations causing that genetic sequence to not be translated into protein or it would favor sequences in which there is a change so that even if that protein is made by accident, the altered sequence would be harmless."
"Pre-selection puts that cryptic variation in a state of readiness," Masel said. "One could think of local solutions as natural selection going on behind the scenes, weeding out variations that are going to be catastrophic, and enriching others that are only slightly bad or even harmless."
"Whatever is left after this process of pre-selection has to be better," she pointed out. "Therefore, populations relying on this strategy have a greater capability to evolve in response to new challenges. With too much proofreading, that pre-selection can't happen."
"Most populations are fairly well adapted and from an evolutionary perspective get no benefit from lots of variation. Having variation in a cryptic form gets around that because the organism doesn't pay a large cost for it, but it's still there if it needs it."
According to Masel, studyi
|Contact: Daniel Stolte|
University of Arizona