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Study the pedigree chart of a… (Class 12 Biology 2024, Q9)

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BiologyCBSE Class 12 · Board exam 2024, set 57/5/1 · 1 mark · MCQ

CBSE Class 12 Biology 2024: question 9

Set in the CBSE Class 12 board exam of 2024, paper 57/5/1, section A, question 9, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q9 · 1 mark · MCQPrinciples of Inheritance and Variation

Study the pedigree chart of a family showing the inheritance pattern of a certain disorder. Select the option that correctly identifies the nature of the trait depicted in the pedigree chart.

  1. (A)Dominant X – linked
  2. (B)Recessive X – linked
  3. (C)Autosomal dominant
  4. (D)Autosomal recessive

Figure in the paper: Pedigree: unaffected parents (square male, circle female) have five children: unaffected son, affected son (filled square), unaffected daughter, affected daughter (filled circle), unaffected son. The unaffected daughter marries an unaffected male and has three children: an affected son (filled square) and two unaffected daughters. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 57/5/1.

Hints

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

Hint 1

Normal parents with affected offspring point to which type of allele?

Hint 2

Could an affected daughter have a normal father if the trait were X-linked recessive?

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 affected children, so the trait is recessive.

  2. An affected daughter is born to an unaffected father, which rules out X-linked recessive inheritance. The trait is therefore autosomal recessive: option (D).

    1 mark

Answer: (D) Autosomal recessive

Where the marks are

  • Concludes autosomal recessive with reasoning (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 paper2024 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.