Friday, January 11, 2008

Blind fish, sighted offspring

From researchers in New York:

Researchers crossed four populations of blind fish from caves in northeast Mexico. Sightless for at least half a million years, the fish evolved from sighted surface fish.

By creating hybrids of the different cave fish populations, researchers found that nearly 40 per cent of some hybrid crosses could see.

The farther apart the caves of the hybrids' parents were, the more likely it was that their offspring could see.

The reason? Sight arises from a combination of genes. Different populations of cave fish had different sets of genes knocked out. One group might have a functioning Gene Set A but a nonfunctioning Gene Set B; another group might have the reverse. Both were blind, but for different reasons.

So when the populations were crossbred, some of the offspring inherited working versions of the full gene set.

From an evolutionary perspective, this illustrates the huge size of the genetic toolbox -- one of the things that makes evolution work, by providing a large number of variables and mechanisms to effect change in an organism. It also highlights one mechanism whereby a major shift -- from sightless to sighted -- could occur in a single generation. It provides a logical basis for rapid evolution in the face of rapid environmental change.

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