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.

A phenotypic trait or disease that resembles the trait expressed by a particular genotype, but in an individual who is not a carrier of that genotype. For example, breast cancer in a hereditary breast/ovarian cancer syndrome family member who does not carry the family’s BRCA1 or BRCA2 mutation would be considered a phenocopy. Such an individual does not have the family’s cancer-related mutation and therefore, they do not have the associated cancer risk from that specific mutation.