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Assertion (A) : In… (Class 12 Biology 2023, Q16)

questionbuddy.in/q/cbse-12-biology-2023-57-5-1-q16-thalassemia-abnormal-myoglobin-chain-synthesized

BiologyCBSE Class 12 · Board exam 2023, set 57/5/1 · 1 mark · Assertion-reason

CBSE Class 12 Biology 2023: question 16

Set in the CBSE Class 12 board exam of 2023, paper 57/5/1, section A, question 16, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q16 · 1 mark · Assertion-reasonCompetency-basedPrinciples of Inheritance and Variation

Assertion (A) : In Thalassemia an abnormal myoglobin chain is synthesized due to a gene defect.
Reason (R) : α-Thalassemia is controlled by genes HBA1 and HBA2 on chromosome 16.

  1. (A)Both (A) and (R) are true and (R) is the correct explanation of (A).
  2. (B)Both (A) and (R) are true, but (R) is not the correct explanation of (A).
  3. (C)(A) is true, but (R) is false.
  4. (D)(A) is false, but (R) is true.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 57/5/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Is the defective protein in thalassemia haemoglobin or myoglobin?

Hint 2

Is the defect in thalassemia a change in the type of chain or in the quantity of chains made?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Thalassemia is a quantitative defect, i.e. too few globin chains of haemoglobin are made. It does not involve an abnormal myoglobin chain, so (A) is false.

    ½ mark

  2. α-thalassemia is controlled by the genes HBA1 and HBA2 on chromosome 16, so (R) is true. Hence option (D).

    ½ mark

Answer: (D)

Where the marks are

  • A false, R true (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Principles of Inheritance and Variation, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 57/5/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.