nonpenetrant trait

non·pen·e·trant trait

a genetic trait that is not phenotypically manifest because of nongenetic factors; it therefore does not include recessivity, epistasis, hypostasis, or parastasis but does include environmental factors and pure random effects such as lyonization.
Farlex Partner Medical Dictionary © Farlex 2012

non·pen·e·trant trait

(non-pen'ĕ-trănt trāt)
A genetic trait that is not phenotypically manifest because of nongenetic factors; it therefore does not include recessivity, epistasis, hypostasis, or parastasis but does include environmental factors and pure random effects such as lyonization.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012