NEET2026BiologyChapterActual
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): In sickle-cell anaemia, the mutant haemoglobin molecule undergoes polymerization under low oxygen tension, causing a change in the shape of the RBC from a biconcave disc to an elongated sickle-like structure. Reason (R): This defect is caused by a single base substitution at the sixth codon of the
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
C. (A) is correct but (R) is not correct
Step-by-step solution
Assertion (A) is correct because in sickle-cell anaemia, the mutant haemoglobin molecule undergoes polymerization under low oxygen tension, which causes the change in the shape of the RBC from a biconcave disc to an elongated sickle-like structure. Reason (R) is incorrect because the defect is caused by a single base substitution at the sixth codon of the -globin gene from GAG to GUG, not from GUG to GAG. This results in the substitution of Glutamic acid (GAG) by Valine (GUG) at the sixth position of the -globin ch