for National Geographic News
European-American populations are less genetically diverse and have more potentially harmful genetic variations than African-American populations, according to an international team of researchers.
The findings suggest that human migrations may have affected genetic diversity and that a population "bottleneck" may have been involved in the original settlement of Europe.
(See a map of ancient human migration.)
Population bottlenecks happen when the size of a certain population shrinks over at least one generation. Over time, the smaller population results in a reduced genetic variation.
The reduced population size sometimes causes mutations that can alter amino acids, the building blocks of proteins.
Researchers led by Carlos Bustamante, a geneticist at Cornell University, analyzed data from 10,000 genes in 35 healthy adults.
Fifteen adults were of African-American origin, and 20 were of European-American origin.
The team found that compared to African Americans, European-American populations had a higher proportion of potentially harmful mutations than was previously thought.
"We predict that in the 10,000 genes we looked at, there are about 400 mutations per individual that are possibly deleterious [or damaging]," said Bustamante, whose findings appear today in the journal Nature.
"Since we have surveyed half the genome, we think the full figure is closer to 800."
"Each of the individuals we studied carry several hundred mutations that likely disrupt protein function," he added.
"The take-home message is there are a lot of likely deleterious variations out there that may be important for disease risk."
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