HbS beta-thalassemia is inherited how?

• A. Inherit HbS from one parent and HbC from the other
• B. Inherit HbS from one parent and HbA from the other
• C. Inherit a gene for haemoglobin S from 1 parent and a gene for beta-thalassemia from the other
• D. Inherit HbS from both parents

Answer: (C)

HbS beta-thalassemia arises when the two beta-globin genes are different mutant alleles: one carries the sickle mutation (HbS) and the other carries a beta-thalassemia mutation. This is a compound heterozygous state in the beta-globin gene and follows autosomal recessive inheritance, so an affected individual inherits one mutant beta-globin gene from each parent. The description “inherit a gene for haemoglobin S from one parent and a gene for beta-thalassemia from the other” captures this scenario precisely. It’s different from inheriting HbS with HbA (which gives sickle cell trait, not HbS beta-thalassemia), HbS with HbC (HbSC disease), or HbS from both parents (HbS/HbS, which is classic sickle cell anemia).