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Assertion: Primary… (Class 12 Biology SQP 2023-24, Q13)

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BiologyCBSE Class 12 · Sample paper, session 2023-24 · 1 mark · Assertion-reason

CBSE Class 12 Biology sample paper 2023-24: question 13

From the official CBSE sample question paper for 2023-24, section A, question 13, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q13 · 1 mark · Assertion-reasonCompetency-basedSexual Reproduction in Flowering Plants

Assertion: Primary endosperm nucleus is diploid.
Reason: It is the product of double fertilisation.

  1. (A)Both A and R are true and R is the correct explanation of A.
  2. (B)Both A and R are true and 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 sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2023-24.

Hints

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

Hint 1

Count how many nuclei fuse to form the PEN.

Hint 2

Each of the two polar nuclei and the male gamete is haploid.

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 primary endosperm nucleus forms when a male gamete fuses with the two polar nuclei (triple fusion), so it is triploid. The assertion is therefore false.

    ½ mark

  2. Triple fusion is one part of double fertilisation, so the reason is true.

    ½ mark

Answer: (D) A is false but R is true

Where the marks are

  • States that the PEN is triploid (0.5 mark)
  • Accepts that it results from double fertilisation (0.5 mark)

Revise the chapter

Practise this chapterBoard-style questions from Sexual Reproduction in Flowering Plants, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2023-24: 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.