Sickle hemoglobin and hemoglobin C variants

The Hb S (sickle cell) variant and Hb C variant are both single point mutations in the gene for beta globin (HBB) that cause a single amino acid change in the beta globin chain. In the heterozygous states, each of these variants causes an essentially asymptomatic carrier state. Homozygosity for Hb S and compound heterozygosity for Hb S plus Hb C cause sickle cell disease. Homozygosity for Hb C causes Hb C disease.

(A) DNA sequence differences.

(B) mRNA sequence differences.

(C) Differences in protein sequence. Each yellow box represents one amino acid. Hb S is designated p.Glu7Val. Hb C is designated p.Glu7Lys.