Scientists map human genetic variations

A new map of the patterns of genetic differences could help speed up the search for genes involved in diseases.

"Humans are 99.9 per cent identical," said Dr. Panos Delousas, a senior investigator on the project at Britain' s Wellcome Trust Sanger Institute.

"It is the tiny percentage that is different that holds the key to why some of us are more susceptible to common diseases such as diabetes or hypertension or respond differently to treatment with certain drugs."

The new "HapMap" charts patterns in human genetic variation throughout the world, making it easier for scientists to identify differences in those affected by disease.

More than 200 researchers from Canada, China, Japan, Nigeria, the United Kingdom and the United States worked on the HapMap, which is described in Thursday's issue of the journal Nature.

The research shows the most common genetic variation, single letter differences called single nucleotide polymorphisms or SNPs, are usually found together in blocks.

Investigators found the blocks, called haplotypes, by analysing DNA samples from 269 volunteers from Nigeria, Japan, China and the U.S.

The haplotypes highlight areas for gene hunters to focus on.

Researchers have already used the data to find a gene linked to the eye disorder macular degeneration, the leading cause of severe vision loss in the elderly.

The map also guided Tom Hudson, director of the McGill University and Genome Quebec Innovation Centre in Montreal, and his team to find a gene that protects some Vietnamese and Brazilian families from leprosy.

The new map will only speed up what's known about how genetics contributes to disease if the variations are common, cautioned David Goldstein and Gianpiero Cavalleri of Duke University wrote in a Nature commentary.

Researchers also need to check if the four population groups studied in the HapMap project reflect variations in other human populations.

A stronger case might be made for identifying differences among patients in response to difference medicines, the pair said.

Canada contributed one-tenth of the funding for the $138-million US project, and Hudson's team generated 10 per cent of the data by analysing chromosomes 2 and 4p of the human genome.