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THE rogue gene that means many people on a remote island in the Pacific see
only shades of grey has been pinpointed. The discovery could eventually help
lead to a cure.

People with achromatopsia can鈥檛 distinguish colours at all. On the
Micronesian island of Pingelap, made famous in Oliver Sacks鈥檚 book The
Island of the Colourblind, 1 in 20 have the disease. Most can trace their
ancestry back to one of the 20 islanders left after a typhoon in 1775. That man
probably carried a single copy of a mutant gene that became common in the tiny,
isolated population.

The gene was known to lurk on a stretch of chromosome 8. Now a team led by
geneticist Olof Sundin of Johns Hopkins University in Baltimore has pinpointed
its position by comparing this sequence to that of a gene which causes similar
symptoms.

The Pingelap gene codes for part of an ion channel in the cone cells in the
retina that detect colour. If the gene is faulty, the cones can鈥檛 produce an
electrical signal when struck by light. 鈥淚 think that within my lifetime there
will be a possibility of treating this with some kind of gene therapy,鈥� says
Sundin.