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New research has found that at least 10 percent of genes in the human population could vary in the number of copies of DNA sequences they contained.
The finding, researchers say could alter current thinking that the DNA of any two humans was 99.9 percent similar in content and identity.
Howard Hughes Medical Institute international research scholar, Stephen W Scherer, and his colleagues discovered that approximately 2,900 genes -- more than 10 percent of the genes in the human genome-had variations in the number of copies of specific DNA segments.
Genes usually occur in two copies, one inherited from each parent.
He believes these differences in copy number could influence gene activity and ultimately an organism's function.
To get a better picture of exactly how important this type of variation is for human evolution and disease, Scherer's team compared DNA from 270 people with Asian, African, or European ancestry that had been compiled in the HapMap collection and
previously used to map the single nucleotide changes in the human genome.
The team mapped the number of duplicated or deleted genes, which they called copy number variations (CNVs).
The team also searched for CNVs using microarray-based genome scanning techniques capable of finding changes at least 1,000 bases (nucleotides) long and found an average of 70 CNVs averaging 250,000 nucleotides in size in each DNA sample.
In all, they identified 1,447 different CNVs that collectively covered about 12 percent of the human genome and six to 19 percent of any given chromosome--far more widespread than previously thought.
The team further found that not only were the changes common, they also were large.
"We'd find missing pieces of DNA, some a million or so nucleotides long. 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," Scherer said.
They also found nearly 16 percent of known disease-related genes in the CNVs, including genes involved in rare genetic disorders such as DiGeorge, Angelman, Williams-Beuren, and Prader-Willi syndromes, as well as those linked with schizophrenia, cataracts, spinal muscular atrophy, and atherosclerosis.
The team believes the findings will change the way researchers think about genetic diseases and human evolution.
They findings appear in the November 23, issue of the journal Nature
ANI