14 March 2008

The High Definition Human Family Tree

This news is three weeks old and doesn't break much new ground, but it still deserves repeating, because it confirms the accuracy of previous population genetics work. It is the first such major study to examine a form of genetic variation known as a "copy-number variant . . .CNVs . . . are large chunks of DNA—up to 1,000,000 consecutive "letters" of the genetic alphabet—that are either repeated or deleted entirely from a person's genome." Some CVNs have been shown to trigger genetic diseases. Previous studies have look only at variations in "letters" and "words" in a person's genomes, not the large chunks of DNA that comprise CNVs.

The latest study characterizes more than 500,000 DNA markers in the human genome and examines variations across 29 populations on five continents [from 485 people] . . . . [it] produced genetic data nearly 100 times more detailed than previous worldwide assessments of human populations. . . . "it's becoming increasingly possible to use genomics to refine the geographic position of an individual's ancestors . . ."

Human genetic diversity decreases as distance from Africa—the cradle of humanity increases. People of African descent are more genetically diverse than Middle Easterners, who are more diverse than Asians and Europeans. Native Americans possess the least-diverse genomes. . . . The results also bolster the notion of "serial founder effects," meaning that as people began migrating eastward from East Africa about 100,000 years ago, each successive wave of migrants carried a subset of the genetic variation held by previous groups.

From here.

No comments: