Select the correct statements about sickle cell anaemia. A. There is a change in gene for beta globin. B. In the beta globin, there is valine in the place of Lysine. C. It is an example of point mutation. D. In the normal gene U is replaced by A. Choose the correct answer from the options given below:

Solution & Explanation

Answer: (B) (A) and (C) only Solution: Statement A is correct (sickle cell anaemia involves a change in the gene for beta globin). Statement C is correct (it is a point mutation, a single base substitution). Statement B is wrong: valine replaces GLUTAMIC ACID, not lysine. Statement D is wrong: the change is at the DNA/codon level GAG to GUG (so within the codon A is replaced by U), not 'U replaced by A in the normal gene'. Hence only A and C are correct, i.e., option (2). NOTE: this differs from the supplied key letter 'B' (option text '(B) and (D) only'), which is inconsistent with NCERT (B and D are both false); option (2) is the NCERT-correct answer. NCERT Reference: NCERT Class XII, Ch 4, p.74-75, p.74 line 19 & p.75 lines 3-6: "This is an autosome linked recessive trait ... (Glu) by Valine (Val) at the sixth position of the beta globin chain of the ... due to the single base substitution at the sixth codon of the beta globin gene from GAG to GUG."