Incomplete Penetrance

Synonyms

Reduced penetrance; Variable expressivity

Definition

Incomplete penetrance occurs when individuals with a certain genotype in a population do not necessarily express the associated phenotype.

Introduction

Incomplete penetrance is a phenomenon of interest to many geneticists, with particular emphasis on disease expression. It occurs in genes of many animals, including humans, and is common with autosomal dominant diseases. However, it can also be found in recessive patterns of heritance, though this is rare. Expression of a phenotype is most likely a result from many factors, including: genetic, environmental, and lifestyle. With a wide variety of factors influencing incomplete penetrance, current research focuses on individual expression of disease phenotypes, as well as carrier genotypes where phenotypic expression may not occur until the next generation of offspring. Incomplete penetrance of genes also renders prediction of disease expression among members of a population or...