Elusive "Pingelapese Blindness" Gene Identified

Before there was Survivor, the hit summer TV show, there was Pingelapese blindness, a classic example of a population bottleneck. In 1775, a typhoon devastated Pengelap, a coral atoll in the Eastern Caroline Islands in Micronesia. Of the 20 survivors, one male passed along a recessive gene for achromatopsia, and four generations later, the condition began to appear, thanks to two centuries of isolation and inevitable inbreeding. In the condition, impaired signal transduction in cone cells leads to total colorblindness, decreased visual acuity, and intense sensitivity to sunlight. Today, frequency among the 3,000 islanders is 5 percent, compared to one in 50,000 to 100,000 individuals here. Researchers from the Johns Hopkins University School of Medicine have identified the causative gene as a cyclic GMP-gated cation channel that normally enables a cone cell to electrically respond to light (O.H. Sundin et al., "Genetic basis of...

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