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When a pure-tall pea plant is… (Class 10 Science 2025, Q9)

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ScienceCBSE Class 10 · Board exam 2025, set 31/4/1 · 1 mark · MCQ

CBSE Class 10 Science 2025: question 9

Set in the CBSE Class 10 board exam of 2025, paper 31/4/1, section A, question 9, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q9 · 1 mark · MCQHeredity

When a pure-tall pea plant is crossed with a pure-dwarf pea plant, the percentage of tall pea plants in and generation pea plants will be respectively :

  1. (A)100% ; 25%
  2. (B)100% ; 50%
  3. (C)100% ; 75%
  4. (D)100% ; 100%

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/4/1.

Hints

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

Hint 1

Write the F1 genotype first.

Hint 2

The F2 phenotype ratio is 3:1.

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. gives an F1 of all , so 100% of plants are tall.

  2. Selfing F1 () gives , so 3/4 = 75% of plants are tall. Option (C).

    1 mark

Answer: (C) 100% ; 75%

Where the marks are

  • 100% and 75% (1 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 paper2025 board paper, set 31/4/1: 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.