What is the difference between continuous and discontinuous variation in genetics?

Continuous variation in genetics refers to traits with a range of small differences, while discontinuous variation refers to traits with distinct categories.

Continuous variation is a type of genetic variation where the individuals in a population vary in small degrees rather than in clear-cut categories. This type of variation is often the result of the combined effect of many genes (polygenic inheritance) and environmental factors. Examples of continuous variation include height, weight, and skin colour in humans. These traits do not fall into distinct categories but rather exist on a continuum. For instance, height in humans is not just tall or short, but a range of heights from the shortest to the tallest person.

On the other hand, discontinuous variation refers to traits that fall into a few distinct categories with little or no intermediate forms. This type of variation is usually the result of the influence of a single gene or a small number of genes. Examples of discontinuous variation include blood type, eye colour, and the presence or absence of certain genetic diseases in humans. These traits are not influenced by the environment and the differences between categories are typically clear-cut. For instance, a person can only have one of the four blood types: A, B, AB, or O.

IB Biology Tutor Summary: Continuous variation involves traits with small, gradual differences influenced by many genes and the environment, like height or skin colour, existing on a scale. Discontinuous variation includes traits that fit into distinct categories, usually controlled by fewer genes, with no middle forms, such as blood type or eye colour. This shows how our genetics can lead to a wide range of physical characteristics.