A copy number variation (CNV) is when the number of copies of a particular gene varies from one individual to the next. Following the completion of the Human Genome Project, it became apparent that the genome experiences gains and losses of genetic material. The extent to which copy number variation contributes to human disease is not yet known. It has long been recognized that some cancers are associated with elevated copy numbers of particular genes.
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Copy number variation is a type of structural variation where you have a stretch of DNA, which is duplicated in some people, and sometimes even triplicated or quadruplicated. And so when you look at that chromosomal region, you will see a variation in the number of copies in normal people. Sometimes those copy number variants include genes, maybe several genes, which may mean that this person has four copies of that gene instead of the usual two, and somebody else has three, and somebody else has five. Interesting, we didn't really expect to see so much of that. It's now turning out to be pretty common, and in some instances, if those genes are involved in functions that are sensitive to the dosage, you might then see a consequence in terms of a disease risk.
Francis S. Collins, M.D., Ph.D.
Director, National Institutes of Health; Former Director, National Human Genome Research Institute
Dr. Francis S. Collins, director of the National Institutes of Health, is noted for his landmark discoveries of disease genes and his visionary leadership of the Human Genome Project, a complex multidisciplinary scientific enterprise directed at mapping and sequencing human DNA. Dr. Collins was the director of the National Human Genome Research Institute from 1993 to 2008. His research has led to the identification of genetic variants associated with type 2 diabetes and the genes responsible for cystic fibrosis, neurofibromatosis, Huntington's disease and Hutchinson-Gilford progeria syndrome. In 2007, Dr. Collins received the Presidential Medal of Freedom, the nation's highest civil award, for his revolutionary contributions to genetic research.