NMAT Biology Practice Test

Polygenic inheritance refers to the genetic situation where multiple genes contribute to a single trait or phenotype. In contrast to traits determined by a single gene, where phenotypes can often be categorized into distinct groups (like blood types or flower colors in certain plants), polygenic traits result in a continuous range of phenotypes.

A hallmark of polygenic inheritance is that the effects of multiple genes combine to produce a smooth gradient of phenotypic expression. This results in the bell-shaped curve commonly associated with normal distribution, where the majority of individuals exhibit intermediate phenotypes, while fewer individuals display extreme traits. For example, human traits such as height, skin color, and weight show continuous variation and fall along the normal distribution curve due to the influence of several genes.

In summary, polygenic inheritance leads to a normal distribution of phenotypes, illustrating the complexity of trait expression that arises from the interplay of multiple genes, each contributing a small effect to the overall phenotype.