what is polygenic inheritance

Polygenic inheritance refers to the kind of inheritance in which a trait is produced from the cumulative effects of many genes. Polygenic traits are characteristics, such as height or skin color, that are influenced by two or more genes. Unlike Mendelian inheritance, where each phenotypic trait is monogenic, meaning the expression of this trait is either dominant or recessive, polygenic inheritance is a multiple factor inheritance or multiple gene inheritance, or multifactorial inheritance. In polygenic inheritance, two or more independent genes additively affect a single phenotypic trait. Polygenic traits do not follow the patterns of Mendelian inheritance, and many polygenic traits are also influenced by the environment and are called multifactorial. The traits that are determined by polygenic inheritance are not simply an effect of dominance and recessivity, and do not exhibit complete dominance as in Mendelian Genetics, where one allele dominates or masks another. Instead, polygenic traits exhibit incomplete dominance so the phenotype displayed in offspring is a mixture of the phenotypes displayed in the parents. Examples of polygenic traits include height, skin color, hair color, blood pressure, intelligence, autism, and longevity.