In an exciting new development, scientists at the Whitehead Institute Center for Genome Research have found that single nucleotide polymorphisms (SNPs) in northern Europeansthe single letter DNA differences that underlie disease susceptibility and individual variationtravel together in blocks that are much larger than previously thought.

The finding has major implications for mapping disease genes and dissecting human population history. It suggests that mapping the genes for common diseases might be much easieras much as 8 times easier in fact-and more manageable and practical than previously thought. It also suggests that it is not necessary for every single SNP to be identified and cataloged before scientists can map genes for human diseases; scientists can embark on this task with the existing collection of SNPs.

Finally, the occurrence of SNPs in large blocks was seen in northern European populations but not seen in the Nigerian populations, suggesting that something happened in the population history of the northern Europeansa recent bottleneck that shaped the genetic history of this population. Scientists speculate that this bottleneck could be related to the founding of Europe or the migration of a small population out of Africa as recently as 50,000 years ago.

"Our results have implications for disease gene mapping, suggesting a possible two-tiered strategy," says Eric Lander, director of the Whitehead Institute Center for Genome Research and one of the leaders of the human genome project. "The large blocks in northern European populations will help us to easily map to first approximation the location of disease genes. And the presence of small blocks in other populations, like the Nigerians we studied, will allow us to hone in on the specific single letter difference responsible for a disease."

The results are published in the May 10 issue of Nature by scientists at the Whitehead Institute and the Institute of Biological Anthropo
'"/>

Contact: Nadia Halim
halim@wi.mit.edu
617-258-9183
Whitehead Institute for Biomedical Research
9-May-2001