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.

genetic heterogeneity
(jeh-NEH-tik HEH-teh-roh-jeh-NEE-ih-tee)
The production of the same or similar phenotypes (observed biochemical, physiological, and morphological characteristics of a person determined by his/her genotype) by different genetic mechanisms. There are two types: (1) allelic heterogeneity – when different alleles at a locus can produce variable expression of a condition; and (2) locus heterogeneity – the term used to describe disease in which mutations at different loci can produce the same disease phenotype.