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.

homozygous genotype
(HOH-moh-ZY-gus JEE-noh-tipe)
Occurs when both alleles at a particular gene locus are the same. A person may be homozygous for the normal allele or for a mutation.