Polygenic Inheritance (Edexcel IGCSE Biology (Modular))

Polygenic Inheritance

• Most characteristics are a result of multiple genes interacting, rather than a single gene

• Characteristics that are controlled by more than one gene are described as being polygenic (poly = many/more than one)

• Polygenic characteristics have phenotypes that can show a wide range of combinations of features

• The inheritance of these polygenic characteristics is called polygenic inheritance 

• Polygenic inheritance is difficult to show using genetic diagrams because of the wide range of combinations

• An example of polygenic inheritance is eye colour – while it is true that brown eyes are dominant to blue eyes, it is not as simple as this as eye colour is controlled by several genes

• This means that there are several different phenotypes beyond brown and blue; green and hazel being two examples