Assertion :Sickle-cell anaemia is an autosomal linked recessive disorder that can be transmitted if both parents are heterozygous for the gene. Reason: In sickle-cell anaemia, haemoglobin molecule undergoes polymerisation under low oxygen tension causing the change in shape of RBC.

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Sickle cell anaemia 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 defect is caused by the substitution of Glutamic ac1d (Glu) by Valine (Val) at the sixth position of the beta globin chain of the haemoglobin molecule. The substitution of amino acid in the globin protein results due to the single base substitution at the sixth codon of the beta globin gene from GAG to GUG. The mutant haemoglobin molecule undergoes polymerisation under low oxygen tension causing the change in the shape of the RBC from biconcave disc to elongated sickle like structure.

So, the correct answer is 'Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion'.