Select the correctly matched pair about sickle cell anaemia :Genotype…

The correct answer is Option (1) → (C) and (D) only

(A) Hb^A Hb^A: Diseased phenotype False. Both alleles are normal. This person makes normal haemoglobin and is healthy.

(B) Hb^A Hb^S: Diseased phenotype False. One normal allele is enough for an apparently unaffected person. The heterozygote is a carrier, not a patient.

(C) Hb^S Hb^S: Diseased phenotype True. In the Hb^S allele, a single base change (GAG to GUG) puts valine in place of glutamic acid at the sixth position of the beta globin chain. With two such alleles, the red blood cells become sickle-shaped under low oxygen.

(D) Hb^S Hb^A: Carrier of disease True. This is the same heterozygous genotype as in (B), written the other way round. The carrier can pass the mutant allele to half of the children.

NCERT Extract:
Mendelian Disorders – “… Sickle-cell anaemia : This is an autosome linked recessive trait that can be transmitted from parents to the offspring when both the partners are carrier for the gene (or heterozygous). The disease is controlled by a single pair of allele, Hb^A and Hb^S. Out of the three possible genotypes only homozygous individuals for Hb^S (Hb^SHb^S) show the diseased phenotype. Heterozygous (Hb^AHb^S) individuals appear apparently unaffected but they are carrier of the disease as there is 50 per cent probability of transmission of the mutant gene to the progeny, thus exhibiting sickle-cell trait ….”