Biology 1201A Lecture Notes - Lecture 3: Natural Disaster, Heterozygote Advantage, Sickle-Cell Disease
Document Summary
Heterozygote advantage: selection in which the heterozygote phenotype has the highest fitness. In order for this to occur the heterozygote phenotype must be different that both homozygous phenotypes. Different alleles for haemoglobin cause red blood cells to not be shaped properly sickle cell. People who have the sickle cell trait technically have lower fitness sickle cell anemia. Homozygotes some have 100% sickle cells, some have 100% normal red blood cells. Heterozygote have both sickle cells and regular cells. In canada there is no heterozygote advantage, but in africa there is a heterozygote advantage. The parasite that causes malaria is good at affecting normal cells but not sickle cells. Individuals that produce sickle cells are less likely to contract malaria. Homozygous normal high chance of contracting malaria, therefore decreased fitness. Homozygous sickle you have sickle cell anemia therefore decreased fitness. Heterozygous just have sickle cell trait, and are less likely to be infected by the malaria parasite, therefore increased fitness.