Polygenic Trait
A polygenic trait is a characteristic influenced by many genes, each with a small effect, resulting in continuous variation like height or facial shape.
A polygenic trait is a phenotypic characteristic influenced by two or more genes, each contributing a small effect to the overall expression. Unlike traits controlled by a single gene, polygenic traits typically show continuous variation across a population, such as height, skin color, or facial structure, and are often further shaped by environmental factors.
What this means in real life
A child's height isn't determined by one gene—dozens of genes from both parents each add or subtract a small amount. Combined with nutrition and health, this creates the continuous range of heights you see in any classroom, rather than everyone being simply 'tall' or 'short.'
What it isn’t
This is not the same as a trait controlled by a single dominant or recessive gene (like ABO blood type or cystic fibrosis). Single-gene traits produce distinct categories; polygenic traits create a spectrum of variation.
Commonly misused online
People often use 'polygenic' to mean 'genetic and environmental,' but the term specifically refers to multiple genes—not the environment. A trait can be polygenic without any environmental influence, though many are both.