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Based on Mendel's experiment… (Class 10 Science 2026, Q13)

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ScienceCBSE Class 10 · Board exam 2026, set 31/5/1 · 3 marks · Short answer

CBSE Class 10 Science 2026: question 13

Set in the CBSE Class 10 board exam of 2026, paper 31/5/1, section A, question 13, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q13 · 3 marks · Short answerHeredity

Based on Mendel's experiment show the cross between round, yellow seeds of pea plant (RRYY) with wrinkled and green seeds of pea plant (rryy) upto generation. Write the number of seeds/plants with following genetic (Genotype) makeup in generation :

  1. (i)

    RRYY

    0 marks
  2. (ii)

    rryy

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/5/1.

Hints

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

Hint 1

First find the F₁ genotype; each parent gives only one kind of gamete.

Hint 2

An RrYy plant makes four kinds of gametes; make a 4 × 4 Punnett square and count the boxes.

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. Parents: Round yellow (RRYY) × Wrinkled green (rryy). Gametes: RY and ry. F₁: all RrYy – round, yellow seeds.

    1 mark

  2. F₁ × F₁ (selfing): RrYy × RrYy. Gametes of each: RY, Ry, rY, ry.

    RYRyrYry
    RYRRYYRRYyRrYYRrYy
    RyRRYyRRyyRrYyRryy
    rYRrYYRrYyrrYYrrYy
    ryRrYyRryyrrYyrryy

    Phenotypic ratio 9 round yellow : 3 round green : 3 wrinkled yellow : 1 wrinkled green.

    1 mark

  3. (i) RRYY – 1 out of 16.

    ½ mark

  4. (ii) rryy – 1 out of 16.

    ½ mark

Answer: F₁ all RrYy (round yellow); F₂ 9:3:3:1; (i) RRYY = 1; (ii) rryy = 1 (out of 16)

Where the marks are

  • Parental cross and F₁ RrYy shown (1 mark)
  • Correct F₂ Punnett square with four gamete types (1 mark)
  • RRYY = 1 (½ mark)
  • rryy = 1 (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Heredity, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 31/5/1: 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.