What kind of inheritance pattern involves multiple genes affecting a single trait?

The concept of polygenic inheritance refers to a situation where multiple genes contribute to the expression of a single phenotype or trait. This is common in traits such as human height, skin color, and eye color, where a combination of alleles from several different genes results in a continuous range of phenotypes.

In polygenic inheritance, each gene may have two or more alleles, and the interactions among these alleles can lead to various shades of the phenotype rather than distinct categories. This is why traits influenced by polygenic inheritance tend to show a bell-shaped distribution in a population.

The other choices, while important genetic concepts, do not describe the influence of multiple genes on a single trait. Codominance involves two alleles that both express themselves fully and independently in the phenotype, while incomplete dominance results in a blend of traits from two alleles. Multiple alleles refer to the existence of more than two alleles for a particular gene, but it does not inherently involve multiple genes affecting a single trait.

Thus, the correct understanding of polygenic inheritance emphasizes how numerous genes contribute to variations in a particular characteristic, leading to a spectrum of phenotypes rather than discrete categories.