Final answer:
Individuals with the HbA HbS genotype do not develop malaria because they have a genetic adaptation to the disease.
Step-by-step explanation:
Individuals with the HbA HbS genotype do not develop malaria because they have a genetic adaptation to the disease. The HbS gene is a single base change in the gene for human beta-hemoglobin and is found in sub-Saharan Africa, the Middle East, and India. It is the most effective genetic adaptation to malaria. The abnormal hemoglobin variant produced by the HbS gene prevents the malaria parasite from causing its effects.
Malaria is a deadly disease caused by the Plasmodium parasite, which is transmitted through mosquito bites. The parasite infects the red blood cells, causing symptoms such as fever, chills, and anemia. However, individuals with the HbA HbS genotype have an advantage in fighting malaria. The abnormal hemoglobin variant present in their red blood cells alters the chemistry and functioning of their blood, making it difficult for the malaria parasite to survive and reproduce. As a result, individuals with this genotype are more resistant to malaria infection.
In contrast, individuals with full-blown sickle cell anemia, who have two copies of the HbS gene, do not have the same protective effect against malaria. Their red blood cells are more prone to sickling, which leads to the symptoms of sickle cell anemia and does not provide immunity to malaria.