Skip to content

Assertion (A) : A male… (Class 12 Biology 2025, Q15)

questionbuddy.in/q/cbse-12-biology-2025-57-7-1-q15-male-individual-always-inherits-haemophilia

BiologyCBSE Class 12 · Board exam 2025, set 57/7/1 · 1 mark · Assertion-reason

CBSE Class 12 Biology 2025: question 15

Set in the CBSE Class 12 board exam of 2025, paper 57/7/1, section A, question 15, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q15 · 1 mark · Assertion-reasonCompetency-basedPrinciples of Inheritance and Variation

Assertion (A) : A male individual always inherits haemophilia from his mother.
Reason (R) : The gene for haemophilia lies on X-chromosome.

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

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 57/7/1.

Hints

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

Hint 1

Which chromosome does a son receive from his father?

Hint 2

Where is the haemophilia gene located?

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. The haemophilia gene is X-linked, so R is true.

  2. A male receives his only X chromosome from his mother (his father gives the Y), so he always inherits haemophilia from her. R therefore explains A. Hence (A).

    1 mark

Answer: (A)

Where the marks are

  • Both true and R explains A (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 paper2025 board paper, set 57/7/1: 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.