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Study the given… (Class 12 Biology SQP 2026-27, Q8)

questionbuddy.in/q/cbse-12-biology-2026-27-sqp-q8-pedigree-identify-disease-represented

BiologyCBSE Class 12 · Sample paper, session 2026-27 · 1 mark · MCQ

CBSE Class 12 Biology sample paper 2026-27: question 8

From the official CBSE sample question paper for 2026-27, section A, question 8, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q8 · 1 mark · MCQCompetency-basedPrinciples of Inheritance and Variation

Study the given pedigree and identify the disease represented

  1. (A)Myotonic Dystrophy
  2. (B)Sickle cell anaemia
  3. (C)Haemophilia
  4. (D)Colour blindness

Figure in the paper: Pedigree chart: normal parents (male square, female circle) have five children: normal male, affected male, normal male, normal female (carrier-like, unshaded), affected female (shaded circle), normal male. The normal male and normal female in the second generation... the unshaded female (marries a normal male) has an affected son (shaded square) and two normal daughters. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

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

Hint 1

Are the parents of the affected children themselves affected?

Hint 2

An affected daughter with a normal father rules out X-linked recessive inheritance.

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. Unaffected parents have both an affected son and an affected daughter, so the trait is recessive and not sex-linked.

  2. An autosomal recessive disease is sickle cell anaemia. Myotonic dystrophy is dominant, while haemophilia and colour blindness are X-linked. Option (B).

    1 mark

Answer: (B) Sickle cell anaemia

Where the marks are

  • Deduces autosomal recessive inheritance and identifies sickle cell anaemia (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 2026-27: 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.