Explain polygenic inheritance pattern with the help of a suitable example.
Human skin colour is an example of polygenic inheritance. It is caused by a pigment called melanin. The quantity of melanin is due to three pairs of polygenes (A, B and C). Very dark or black colour is due to the presence of dominant alleles (AABBCC). Very light or dark colour is due to the presence of all recessive alleles (aabbcc). Intermediate colour is often shown in the F1 generation when a dark or a black colour individual marries a white colour individual. Such an offspring is called mulatto (AaBbCc). When two such individuals of intermediate colour marry, the skin colour of the children will vary from the very dark or black to the very light or white.