An environmentally caused phenotype that mimics a genetic trait. For example, epilepsy can be caused by mutations in single genes (with genetic heterogeneity), and, among other causes, by brain injury, which produces a phenocopy of genetic epilepsy.
A phenocopy is an individual whose phenotype (generally referring to a single trait), under a particular environmental condition, is identical to the one of another individual whose phenotype is determined by the genotype. In other words the phenocopy environmental condition mimics the phenotype produced by a gene.