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Albinism is known to be… (Class 12 Biology SQP 2025-26, Q7)

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BiologyCBSE Class 12 · Sample paper, session 2025-26 · 1 mark · MCQ

CBSE Class 12 Biology sample paper 2025-26: question 7

From the official CBSE sample question paper for 2025-26, section A, question 7, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q7 · 1 mark · MCQPrinciples of Inheritance and Variation

Albinism is known to be due to an autosomal recessive mutation. The first child of a couple with normal skin pigmentation was an albino. What is the probability that their second child will also be an albino?

  1. (A)100%
  2. (B)25%
  3. (C)50%
  4. (D)75%

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.

Hints

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

Hint 1

What must the parents' genotypes be?

Hint 2

Each birth is an independent event.

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. Normal parents having an albino (aa) child must both be carriers, Aa.

  2. gives AA : Aa : aa = 1 : 2 : 1, so probability of aa for each child = 1/4 = 25% (independent of the first child). Answer (B).

    1 mark

Answer: (B) 25%

Where the marks are

  • Deduces both parents Aa and gets 25% (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 paperSample paper 2025-26: 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.