Polygenic Traits

When multiple genes act together to influence a phenotype, the result is called a polygenic trait, a trait controlled by many genes.

One such characteristic is human height, which is influenced by many genes located on different chromosomes.

Although each gene usually has only a small role in regulating growth during development, the combined effects of these genes determine how tall a person will be in adulthood.

Because many genes influence human height, it varies considerably among individuals.

For instance, the minimum height of adult females in a population might be about five feet, while the maximum is about six feet.

However, women with heights between these two extremes also exist.

When this height distribution is graphed, it shows a bell-shaped curve.

Most individuals inherit combinations of height-influencing genes that result in intermediate heights, while relatively few inherit combinations that result in shorter or taller heights. Only a few women reach the minimum or maximum height, and most are near the average height of five and a half feet.

This pattern also applies to many other polygenic traits, such as weight, blood pressure, and even the number of ridges in fingerprints.