Final answer:
The ethnic group with the highest incidence of sickle cell disease is those of African descent, especially African Americans. The presence of the sickle cell allele offers resistance to malaria, hence its prevalence in areas affected by the disease. Despite the associated health challenges, this genetic adaptation continues to be prevalent in these populations.
Step-by-step explanation:
Incidence of Sickle Cell Disease
The ethnic group with the highest incidence of sickle cell disease is those of African descent, particularly among African Americans. Data indicates that 8-10% of African Americans are affected by sickle cell disease or carry the sickle cell trait, with a significant number of cases also found in Africa, India, and Saudi Arabia. The prevalence is particularly high in regions where malaria is or was prevalent, as individuals with one sickle cell allele (heterozygotes) have a survival advantage due to resistance to malaria. This evolutionary benefit helps maintain the allele within the population despite the health challenges posed by the homozygous state of the disease.
For those who are homozygous for the sickle cell trait, they exhibit symptoms associated with sickle cell anemia, where red blood cells have a characteristic crescent shape causing complications such as blocked blood vessels and tissue damage. This genetic disorder, therefore, has a complex relationship with natural selection and disease prevalence among different populations.