Final answer:
Polygenic inheritance is when a trait is governed by multiple genes, leading to a broad range of phenotypes within a population, often forming a bell-shaped distribution curve. Height and skin color are classical examples of polygenic traits.
Step-by-step explanation:
Polygenic inheritance refers to the phenomenon where a single trait is controlled by multiple genes. Unlike single-gene (Mendelian) traits, polygenic traits result from the cumulative effect of multiple genes working together, each contributing to the overall expression of that trait. Traits like height, skin color, eye color, and weight are all examples of polygenic inheritance, showcasing a broad spectrum of phenotypic outcomes. To identify polygenic inheritance, one would look for a trait that exhibits a continuous range of variations within a population, often forming a bell-shaped curve when the phenotypes are graphed. A notable example of a polygenic human disease would be type 2 diabetes, which results from the combined influence of genes related to metabolism, pancreatic function, and insulin sensitivity. Eye color is another classic example of a polygenic trait. Contrary to common teaching that suggests it's determined by a single gene, eye color results from the interplay of several genes affecting melanin levels. Albinos, for instance, lack melanin, which means that they would not have dark eyes. Individuals with blue eyes have lower levels of melanin than those with darker eyes. In a population, polygenic traits typically result in a variety of phenotypes, which can be numerous due to the different possible combinations of alleles across the genes involved. For instance, height can be influenced by at least three genes, each with two alleles, resulting in many possible height outcomes from very short to very tall.