Polygenic trait
A trait controlled by many genes, often plus the environment. These traits vary continuously, giving a bell-shaped spread rather than clear categories.
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Analogy
A mixing desk with many sliders, not one switch.
In practice
Human height and skin colour. Genes set the range and nutrition affects where within it a person ends up.
Practice
Flashcards
- What kind of variation does a polygenic trait show?Continuous variation, a smooth bell-shaped spread.
Questions people ask
Why are traits like height not simple 3:1 ratios?
Height depends on many genes, each adding a small effect, and on the environment, such as nutrition. With many gene combinations possible, people fall along a smooth range rather than in clear groups. Plotting heights in a large group gives a bell-shaped curve.
Does the environment affect gene expression?
Yes. Genes set a range of possibilities, and the environment influences where within it an individual ends up. A child with genes for tall height may not reach it with poor nutrition. Identical twins raised apart can differ in weight, health and skills because of their different environments.