Explain the heterozygote advantage of the sickle cell β-globin allele in areas where malaria is prevalent
The heterozygote advantage of the sickle cell β-globin allele refers to the fact that individuals who inherit one copy of the sickle cell gene and one normal copy have a selective advantage in areas where malaria is prevalent. This is because the sickle cell gene also confers some resistance against malaria infection.
Malaria is caused by a parasite called Plasmodium, which is transmitted to humans through mosquito bites. The parasite infects and destroys red blood cells, leading to anemia and other complications. However, individuals with the sickle cell trait (heterozygous for the sickle cell gene) have red blood cells that are less hospitable to the malaria parasite. This is because the sickle cell gene causes red blood cells to become less flexible and curved, making it difficult for the parasite to invade and multiply.
Therefore, individuals who carry the sickle cell trait are less likely to develop severe malaria symptoms and are more likely to survive the infection. This gives them a selective advantage over individuals who do not carry the sickle cell gene at all.
However, individuals who inherit two copies of the sickle cell gene (homozygous for the sickle cell gene) develop sickle cell disease, which is a serious and sometimes fatal condition. Therefore, the heterozygote advantage of the sickle cell gene is only observed in individuals who carry one copy of the gene and one normal copy.