TUESDAY, March 24, 2009 (HealthDay News) -- U.S. researchers have identified 1,362 copy number variations (CNVs) in the human genome of blacks and 1,972 in whites.
CNVs -- differences in gene copy numbers caused by deletions, duplications or rearrangements of genomic regions -- account for a large amount of human diversity and can also be associated with behavioral traits or increased susceptibility to a disease.
Across the genome, there was little difference in the frequency of CNVs between blacks and whites. However, there was a marked difference in the frequency of two duplications, one on chromosome 15 and another on chromosome 17, said Joseph P. McElroy and his colleagues in the neurology department at the University of California, San Francisco.
A duplication in chromosome 17 (region 17q21) was found in 45 percent of the 435 whites in the study and in 8 percent of the 435 blacks. This region has been implicated in mental retardation caused by the deletion of two genes due to duplication. The two genes aren't located within the 17q21 region, but are very close to it, the researchers said.
"It would be good to know if the CNV duplication of the region might have an effect on the expression of these genes, which in turn could result in neurological disease. It is also interesting to find out whether the type of mental retardation associated with this locus is more common in whites than in Africans or African-Americans. If this is true, then it might be one of the first reported diseases with differing ethnic frequencies due to CNVs," McElroy said in a news release.
The study was published March 23 in the journal BMC Genetics.
"To the best of our knowledge, this is the first detailed map of copy number variations in African-Americans. Understanding the distribution of CNVs in a population is a first step to addressing their role in disease," McElroy said.
The U.S. National Institute of General Medical Sciences has more about human genetic variation.