What defines a polygenic trait?

A polygenic trait is characterized by being influenced by multiple genes, which work together to produce a continuous range of phenotypes. This complex interaction allows for a significant variety of expressions of a trait within a population, often resulting in traits that cannot be easily categorized into distinct categories, such as height, skin color, or intelligence.

The correct answer highlights the complexity of polygenic traits, as they are not determined by a single gene, making them fundamentally different from traits governed by monogenic inheritance, where one gene dictates a trait's expression. In addition, polygenic traits often demonstrate additive effects, meaning that the contributions of multiple alleles can enhance or diminish the overall phenotype.

By understanding the nature of polygenic traits, one can appreciate how traits can vary widely and how they are influenced not only by genetic makeup but also by environmental factors. However, the essence of a polygenic trait lies in its dependence on several genes rather than a single genetic influence, which is key to distinguishing it from other types of traits.