Final answer:
Human traits are commonly controlled by multiple genes through polygenic inheritance, leading to a wide range of variation in characteristics such as height, skin color, and weight.
Step-by-step explanation:
Polygenic Traits in Humans
Most traits in humans are not determined by a single gene, but are the result of polygenic inheritance, where a trait is controlled by more than one gene. This complex interaction between multiple genes, where each gene can have multiple alleles, gives rise to the wide variation we see in many traits such as height, skin color, and weight. Unlike Mendelian traits, which are influenced by a single gene, polygenic traits can be measured and often show continuous variation across a range.
For example, height is a classic polygenic trait, influenced by at least three genes with six alleles. Dominance in these alleles can lead to a taller stature. Similarly, a diversity of skin colors exists because skin color is also a polygenic trait, controlled by multiple genes. Environmental factors can further influence these traits, adding to their variability.
Understanding that most human traits are polygenic is critical, as it explains the genetic diversity necessary for the survival of a species. When environmental factors reduce the gene pool, it can put a species at risk of extinction due to the loss of this diversity.