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Gene Isolated for Colorblindness

July 31, 1998

FRANKFURT, Germany (AP) _ Researchers at Tuebingen University in southern Germany say that they have isolated the defective gene that causes full colorblindness.

The discovery means that potential parents will be able to find out whether they carry the recessive trait that causes the rare inherited disorder, called rod monochromacy. Eventually, it could lead to gene therapy to treat the colorblindness, researchers said.

People with rod monochromacy cannot sense any colors from birth, seeing only various shades of gray.

About one in 50,000 people suffers from the disorder, chronicled by Oliver Sacks in his 1997 book ``The Island of the Colorblind,″ about the Micronesian island of Pingelap where 10 percent of the inhabitants are fully colorblind.

German geneticist Bernd Wissinger and Canadian vision scientist Lindsay Sharp said their research, published in this month’s New York-based Nature Genetics journal, involved tests on colorblind people in Germany, Norway, Italy and the United States.

Sharp said the team isolated a gene mutation on Chromosome 2 that blocks light reception in parts of the eye’s retina known as cones.

``We just happened to be focusing on this particular gene, and in a sense got lucky,″ Sharp said, adding that other researchers have been looking for the gene. ``There is always a race going on in molecular genetics.″

The mutation affects reception in each of the three cones linked with the sensation of red, green and blue light. The defective gene blocks the production of a cell component necessary for the cones to function properly, Sharp said.

Sharp said he could not rule out the existence of other defective genes capable of causing the same disorder.

Joel Pokorny, a colorblindness expert at the University of Chicago, said the Tuebingen research represented ``an interesting find.″

``If you have an understanding of what the genetics are, you can maybe at some point find a treatment,″ Pokorny said.

Though babies with full colorblindness often show symptoms of the disorder almost immediately, isolating the gene responsible will allow doctors to confirm the presence of the disorder earlier, Sharp said.

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