Skip to content

Answer the following. (Science 2025 31/1/1 Q30)

questionbuddy.in/q/cbse-10-science-2025-31-1-1-q30

ScienceCBSE Class 10 · Board exam 2025, set 31/1/1 · 3 marks · Short answer

CBSE Class 10 Science 2025: question 30

Set in the CBSE Class 10 board exam of 2025, paper 31/1/1, section C, question 30, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q30 · 3 marks · Short answerHeredity

Answer the following.

  1. (a)

    What are chromosomes?

    0 marks
  2. (b)

    Explain in brief how stability of DNA content of a species is ensured in sexually reproducing organisms?

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/1/1.

Hints

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

Hint 1

If gametes had the full chromosome number, what would happen to the zygote each generation?

Hint 2

Think about halving and then restoring.

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. (a) Chromosomes are thread-like structures in the nucleus. They are made of DNA, which carries genes, the information for inheritance of features from parents to the next generation.

    1 mark

  2. (b) Each body cell has two copies of each chromosome, one from each parent. During gamete (germ cell) formation, the chromosome number is halved, so each gamete gets only one set.

    1 mark

  3. (b) When the male and female gametes fuse during fertilisation, the zygote formed gets one set from each. This restores the original number of chromosomes, so the DNA content of the species stays the same from generation to generation.

    1 mark

Answer: (a) DNA-containing structures in the nucleus carrying genes; (b) gametes have half the chromosomes, and fusion restores the full number in the zygote, keeping DNA content constant

Where the marks are

  • Chromosomes carry genes/DNA for inheritance (1 mark)
  • Chromosome number halved during gamete formation (1 mark)
  • Fusion of gametes restores the normal number in the zygote (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 paper2025 board paper, set 31/1/1: 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.