phenocopy /fē″nōkop′ē/ [Gk, phainein, to appear; L, copia, plenty] , a phenotypic trait or condition that is induced by environmental factors but closely resembles a phenotype usually produced by a specific genotype. The trait is neither inherited nor transmitted to offspring. Such conditions as deafness, cretinism, cognitive impairment, and congenital cataracts are caused by mutant genes but can also result from a number of different agents, such as the rubella virus in the case of congenital cataracts. Because phenocopies may present problems in genetic screening and genetic counseling, all exogenous factors must be ruled out before any congenital trait or defect is labeled hereditary.
