NCI Dictionary of Genetics Terms
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.
- One of two or more DNA sequences occurring at a particular gene locus. Typically one allele (“normal” DNA sequence) is common, and other alleles (mutations) are rare.