NCI Dictionary of Genetics Terms

The NCI Dictionary of Genetics Terms contains technical definitions for more than 200 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.

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hemizygous
(HEH-mee-ZY-gus)
Describes an individual who has only one member of a chromosome pair or chromosome segment rather than the usual two. Hemizygosity is often used to describe X-linked genes in males who have only one X chromosome. This term is sometimes used in somatic cell genetics where cancer cell lines are often hemizygous for certain alleles or chromosomal regions.