We’re more genetically diverse than thought: study
Nov. 23, 2006
Special to World Science
Special to World Science
New research has found that at least 10 percent of genes in the
human population can vary in the number of copies of certain DNA sequences.
The findings undermine a popular view that the DNA of any two humans is 99.9 percent alike, researchers said. That idea is widespread; scientists still sometimes cite it as evidence that there are no significant differences among races, although recent research has cast doubt on both notions.
The findings undermine a popular view that the DNA of any two humans is 99.9 percent alike, researchers said. That idea is widespread; scientists still sometimes cite it as evidence that there are no significant differences among races, although recent research has cast doubt on both notions.
The new findings, from geneticist Stephen
W. Scherer of the University of Toronto and its affiliated Hospital
for Sick Children, could also reshape thinking on genetic diseases and
evolution, scientists say.
Genes usually occur in two copies, one inherited from each parent. Scherer and colleagues found some 2,900 genes—more than 10 percent of those in the genome—with variations in the number of copies of specific DNA segments.
These differences can affect gene activity and biological functions, the group said.
To understand the implications for human evolution and disease, Scherer’s team compared DNA from 270 people of Asian, African, or European ancestry. The investigators mapped the number of duplicated or deleted genes, which they call copy number variations. They reported the findings in the Nov. 23 issue of the research journal Nature.
The researchers searched for the variations using microarrays, a genome scanning technology that can find changes at least 1,000 nucleotides, or “letters” of genetic code, in length. They found an average of 70 of these regions, averaging 250,000 nucleotides long, in each sample. In all, the group identified 1,447 different copy number variations collectively covering about 12 percent of the genome and six to 19 percent of any given chromosome.
Not only were the changes common, they also were large, Scherer said. “We’d find missing pieces of DNA, some a million or so nucleotides long,” he added. “We used to think that if you had big changes like this, then they must be involved in disease. But we are showing that we can all have these changes.”
Genes usually occur in two copies, one inherited from each parent. Scherer and colleagues found some 2,900 genes—more than 10 percent of those in the genome—with variations in the number of copies of specific DNA segments.
These differences can affect gene activity and biological functions, the group said.
To understand the implications for human evolution and disease, Scherer’s team compared DNA from 270 people of Asian, African, or European ancestry. The investigators mapped the number of duplicated or deleted genes, which they call copy number variations. They reported the findings in the Nov. 23 issue of the research journal Nature.
The researchers searched for the variations using microarrays, a genome scanning technology that can find changes at least 1,000 nucleotides, or “letters” of genetic code, in length. They found an average of 70 of these regions, averaging 250,000 nucleotides long, in each sample. In all, the group identified 1,447 different copy number variations collectively covering about 12 percent of the genome and six to 19 percent of any given chromosome.
Not only were the changes common, they also were large, Scherer said. “We’d find missing pieces of DNA, some a million or so nucleotides long,” he added. “We used to think that if you had big changes like this, then they must be involved in disease. But we are showing that we can all have these changes.”
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