The more detailed description of genetic variations is expected later this year from the international HapMap Project, directed by government agencies from Japan, China and Canada, as well as The Wellcome Trust of London and the U.S. National Institutes of Health. That mapping effort will describe variation across individuals of Japanese, Chinese, Nigerian and European ancestry, said Cox, who also works with the public group.

Navigating the Genome

Around the world, life's genetic blueprint is 99.99 percent similar from person to person, with the greatest degree of variation found inside Africa, where DNA has been evolving for the longest period of time. But, single-letter variations, called "snips," for single-nucleotide polymorphisms (SNPs), may determine each person's disease-vulnerability and response to different medications, as well as a broad range of other traits, from eye color and height to hair color and body type. The relationship between such traits and single DNA-letter variations is poorly understood, though, and scientists also know little about the importance of common versus rare SNPs. An estimated 7 million common SNPs can be found within 5 percent of the entire human population, the Science paper notes. Another 4 million SNPs are far less common, turning up in only 1 percent to 5 percent of the world's entire population. Still more rare DNA variations may be found only in a single individual.

To investigate genetic variation, the Science authors took advantage of patterns among interconnected SNPs. A small, known section of genetic code containing a SNP can be used to predict larger, related chunks of sequence, and thus, provides a shortcut for mapping whole-genome patterns of genetic variations shared by people of European American, African American and Han Chinese American ancestry.

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17-Feb-2005