Final answer:
A polygenic trait is controlled by multiple genes and can result in many genotypes and a wide range of phenotypes. Examples include height and skin color, which exhibit continuous variation and a bell-shaped distribution in the population.
Step-by-step explanation:
A polygenic trait often has many possible genotypes and even more different phenotypes. Polygenic traits are traits controlled by more than one gene, with each gene having multiple alleles possible. This means that the combinations of alleles can result in a wide variety of phenotypes. For example, human skin color is a polygenic trait with many potential genotypes leading to a spectrum of skin colors.
The concept of multiple alleles essentially means that, although an individual organism can only have two alleles for a given gene, at the population level there can be a wide variety of alleles present. The most common genotype or phenotype is referred to as the wild type, and variants of this are either dominant or recessive to the wild-type allele. Traits like height, skin color, hair color, and eye color are all examples of polygenic traits, which often result in a bell-shaped distribution of the trait across a population.
It's important to understand that the majority of human traits are polygenic rather than Mendelian. This is due to the fact that single traits are often the result of the interaction of multiple genes, and the traits can often be measured on a continuum and can be influenced by environmental factors, as well.