Researchers have mapped the most common genetic differences across the entire genome for 269 different humans in unprecedented detail. A study in the 27 Oct 05 issue of Nature (Vol. 437, No. 7063, pp. 1299-1320) presents a map of these differences, and a second study (pp. 1365-1369) uses this data set to identify places in the genome where certain genes are regulated.
The goal is to understand the complex genetic changes that underlie common diseases such as cardiovascular disease, cancer, or psychiatric illnesses, which are still largely unknown. Researchers believe that a big part of the answer lies in tiny changes in the DNA sequence, called single nucleotide polymorphisms (SNPs). These are single-letter differences in the DNA between individuals.
An international team of researchers led by David Altshuler and Peter Donnelly present a map of more than one million of the most common SNPs grouped into haplotypes - combinations of SNPs that have travelled together over evolutionary time. The team checked SNPs from 269 people from four different populations: 90 people from Nigeria, 90 from the United States, 45 from China and 44 from Japan.
This information will make it unnecessary to sequence the entire genome to find SNPs that are associated with certain diseases. This is because SNPs are inherited in groups or haplotypes. To identify a SNP associated with a certain disease, all researchers have to do is to associate that disease with a certain haplotype. They can then analyse that haplotype further to identify the exact SNP that is the cause for the disease.
In the second paper, Vivian Cheung and colleagues have used this large data set to find associations between certain SNPs and the levels at which certain genes are expressed. They identify the exact DNA sequence that controls the expression levels of one gene. It should be possible to use this approach to understand the genetic causes of traits such as blood pressure and obesity, they say. A related News & Views article by David B. Goldstein and Gianpiero L. Cavalleri accompanies this work.
David Altshuler (The Broad Institute of Harvard and Massachusetts Institute of Technology, Cambridge, MA, USA. Also at: Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA) paper no: 
Vivian G. Cheung (University of Pennsylvania and The Children's Hospital of Philadelphia, Philadelphia, PA, USA) paper no: 
David B. Goldstein (Duke University, Durham, NC, USA)
(C) Nature press release.
Message posted by: Trevor M. D'Souza