How does polygenic inheritance affect phenotypes?

Polygenic inheritance occurs when a single trait is controlled by multiple genes, each contributing a small additive effect. This results in continuous variation in phenotypes rather than distinct categories.

In such traits, no single gene determines the outcome. Instead, several genes (called polygenes) work together, and their combined effect influences the final phenotype. Each dominant allele typically adds to the expression of the trait, while recessive alleles contribute less or not at all.

Common examples include height, skin color, weight, and intelligence, where a wide range of variations is observed within a population. These traits often show a bell-shaped distribution curve, reflecting gradual differences rather than clear-cut groups.

Environmental factors also interact with genetic factors in polygenic inheritance. For example, nutrition can influence height, and sunlight exposure can affect skin pigmentation.

Because multiple genes are involved, predicting inheritance patterns becomes more complex compared to single-gene traits.

Overall, polygenic inheritance explains the continuous variation seen in many human traits and highlights the combined influence of multiple genes and environmental factors.