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"Stability of DNA in a… (Class 10 Science 2024, Q23)

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ScienceCBSE Class 10 · Board exam 2024, set 31/2/1 · 2 marks · Very short answer

CBSE Class 10 Science 2024: question 23

Set in the CBSE Class 10 board exam of 2024, paper 31/2/1, section B, question 23, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q23 · 2 marks · Very short answerHeredity

"Stability of DNA in a species is ensured during sexual reproduction." Justify the statement.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/2/1.

Hints

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

Hint 1

How many chromosomes does a gamete have compared with a body cell?

Hint 2

What happens to the chromosome number when two gametes fuse?

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. Germ cells are made by a special division, so each germ cell gets only one chromosome from each pair. That chromosome may be of maternal or paternal origin, so a gamete has half the number of chromosomes and half the DNA.

    1 mark

  2. When the male and female gametes fuse at fertilisation, the zygote gets back the full original number of chromosomes. So the chromosome number and DNA content stay the same from generation to generation, which keeps the DNA of the species stable.

    1 mark

Answer: Gametes carry half the chromosomes (one of each pair); their fusion restores the original number, keeping DNA content constant in the species.

Where the marks are

  • Gametes receive one chromosome from each pair, i.e. half the number (1 mark)
  • Fusion at fertilisation restores the original number, keeping DNA stable (1 mark)

Revise the chapter

  • Chapter: Heredity (notes, formulas, where marks are lost and every past question)
Practise this chapterBoard-style questions from Heredity, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 31/2/1: 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.