In genetics, what does it mean if a trait is described as polygenic?

A trait described as polygenic means that it is influenced by multiple genes, each contributing to the overall phenotype. In polygenic inheritance, these genes may be located on different chromosomes and can interact in complex ways to produce a continuous range of traits. For example, traits like height, skin color, and intelligence show variation that cannot be attributed to a single gene but rather to the combined effects of several genes, each with its own alleles.

The distinction between polygenic traits and those controlled by a single gene is important in genetics. Single-gene traits tend to have a much clearer manifestation, often showing a dominant-recessive pattern, while polygenic traits exhibit more subtle variations since each contributing gene adds to the trait's expression. This complexity can lead to a spectrum of phenotypes in the population rather than discrete categories.

Other terms, such as multiple alleles or influencing multiple traits, do not accurately capture the essence of polygenic inheritance. Multiple alleles refer to variations of a particular gene, and traits influencing multiple characteristics suggest pleiotropy, which is a different concept where one gene affects more than one trait. Therefore, the correct understanding of polygenic traits is that they involve multiple genes contributing collectively to a particular phenotype.