In polygenic inheritance, several sets of alleles may produce cumulative effect on the same character. eg, human height and skin colour. ABO blood group in humans is an example of codominance, whereas flower colour in Mirabilis jalapa (four O clock plant) is an example of incomplete dominance. Hair pigment of mouse is an example of recessive epistasis. Human eye colour is an example of polygenic inheritance, whereas sickle cell anaemia is an example of codominance.