What is the result of a genetic defect variant known as hemoglobin S?

• A. Iron deficiency anemia
• B. Hemolytic anemia
• C. Pernicious anemia
• D. Sickle cell anemia

Answer: (D)

Hemoglobin S is a variant of hemoglobin that arises from a genetic mutation where there is a substitution of valine for glutamic acid at the sixth position of the beta-globin chain. This alteration leads to the production of abnormal hemoglobin, which can distort red blood cells into a characteristic sickle shape under low oxygen conditions.

The sickle-shaped cells are more rigid and can block blood flow in small vessels, leading to a range of complications including pain crises, increased risk of infection, and chronic hemolytic anemia due to the breakdown of damaged red blood cells. This condition is specifically known as sickle cell anemia, which stems directly from the presence of hemoglobin S. Therefore, identifying this genetic defect as a cause of sickle cell anemia is essential, as it directly correlates to abnormal hemoglobin structure and function.

This is why the answer related to sickle cell anemia is the correct choice, as it specifically indicates the condition associated with the presence of hemoglobin S.