Final answer:
Sickle cell anemia is a hereditary blood disorder caused by abnormal hemoglobin leading to sickle-shaped red blood cells. The disease is inherited in an autosomal recessive pattern, giving a 25% chance of an affected child if both parents are carriers of the mutated gene. The sickle cell trait persists in some populations due to its protective benefits against malaria.
Step-by-step explanation:
Sickle Cell Anemia and Genetics
Sickle cell anemia is an autosomal recessive blood disorder characterized by the production of abnormal hemoglobin, which leads to the sickle or crescent shape of red blood cells. This shape change in red blood cells causes them to get stuck in blood vessels, obstructing blood flow, which can lead to symptoms such as severe pain, swelling, and tissue damage. Parents with a genetic mutation for sickle cell anemia can pass this trait to their offspring. If two carriers have children, there is a 25% chance of the child being affected, a 50% chance of the child being a carrier (asymptomatic), and a 25% chance of the child being unaffected. This is due to the Mendelian principle of inheritance where each parent carries one normal allele (A) and one mutated allele (S).
The prevalence of the sickle cell trait in certain populations, such as those of African descent, remains significant despite its harmful effects due to its protective benefit against malaria. Heterozygous carriers are less prone to malaria, which outweighs the selective pressure against the sickle cell anemia in regions where malaria is endemic. Consequently, the trait persists due to the survival advantage it confers in those specific geographic areas.