NCI Dictionary of Genetics Terms

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Welcome to the NCI Dictionary of Genetics Terms, which contains technical definitions for more than 150 terms related to genetics. These definitions were developed by the PDQ® Cancer Genetics Editorial Board to support the evidence-based, peer-reviewed PDQ cancer genetics information summaries.

copy number variant
(KAH-pee NUM-ber VAYR-ee-unt)
Refers to the genetic trait involving the number of copies of a particular gene present in the genome of an individual. Genetic variants, including insertions, deletions, and duplications of segments of DNA, are also collectively referred to as copy number variants. Copy number variants account for a significant proportion of the genetic variation between individuals. Also called CNV.