Last Updated: Monday, January 7, 2008 | 1:06 PM ET
CBC News
Cross-breeding blind cave fish with those from separate populations of blind cave fish can partially restore their vision, overriding half a million years of evolutionary change, say U.S. scientists.
"These fish are descended from ancestors that have been isolated in the dark for nearly one million years and most likely haven't had the capacity for vision for at least half that time," New York University biology professor Richard Borowsky, the study's lead author, said in a release.
"But by recombining the right genes through hybridization, you can partially restore vision. Not only are the structures of the eye restored to the point where they regain function, but all the connections to the brain for proper processing of information not used for that enormous length of time are restored."
The finding, which may have implications for understanding human eyes, was published in Monday's issue of the journal Current Biology.
The study suggests that genetic engineering can override, at least in part, evolutionary change in just one generation. That's because mutations in different genes are responsible for the loss of sight in separate cavefish lineages.
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Blind cave fish see the light
By mating blind fish from distant underwater caves, researchers have bred offspring that can see.
The results, published this week in Current Biology 1, show that the two populations took different evolutionary paths to blindness.
“We’ve basically shown that these different populations have converged upon the same outward appearance independently, and that they use different genes to do it,” says Richard Bolowsky of New York University.
The blind fish, called Astyanax mexicanus , live in isolated limestone caves in northeast Mexico. Over hundreds of millennia of living in darkness, the fish, which have a sighted ancestor, accumulated genetic mutations that affect eye development, and so lost their sight. Today some 29 different varieties of the blind Mexican fish live in isolated caves. Researchers have long wondered whether they all lost their sight the same way or not.
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