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NEETZoologyPrinciples of Inheritance and Variation

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 high oxygen tension, causing the change in the shape of the RBC. Reason (R): The disease is caused by the substitution of glutamic acid by valine at the sixth position of the beta globin chain of the haemoglobin

Options

  1. ABoth Assertion and Reason are true and Reason is the correct explanation of Assertion
  2. BBoth Assertion and Reason are true but Reason is not the correct explanation of Assertion
  3. CAssertion is true but Reason is false
  4. DAssertion is false but Reason is true

Correct answer

D. Assertion is false but Reason is true

Step-by-step solution

Assertion (A) is false because the mutant haemoglobin molecule (HbS) undergoes polymerization under low oxygen tension, not high oxygen tension. This polymerization causes the biconcave disc shape of the RBC to change into an elongated sickle-like structure. Reason (R) is true as sickle cell anaemia is indeed caused by the substitution of glutamic acid by valine at the sixth position of the beta globin chain of the haemoglobin molecule. Therefore, Assertion is false but Reason is true. Answer: Assertion is false bu

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