- Inheritance of one sickle cell allele is known as sickle cell trait, while inheritance of two causes sickle cell anemia.
(a) Outline how a base substitution leads to sickle cell anemia. [4]
(b) Construct a Punnett grid to show how two parents with no symptoms can have a child with sickle cell anemia. [4]
(c) Sickle cell trait offers some protection against malaria, which is carried by mosquitoes. Explain how sickle cell trait evolved in countries such as Kenya, where mosquitoes are common, even though sickle cell anemia can be lethal. [7]