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Show the cross and… (Class 10 Science 2026, Q14)

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

CBSE Class 10 Science 2026: question 14

Set in the CBSE Class 10 board exam of 2026, paper 31/3/1, section A, question 14, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q14 · 3 marks · Short answerHeredity

Show the cross and observations made by Mendel when he crossed pure tall pea plant with a pure short pea plant to get progeny.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/3/1.

Hints

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

Hint 1

Write the pure tall plant as TT and the pure short plant as tt. What gametes can each make?

Hint 2

Combine the gametes. Which trait shows when both T and t are present, and were any plants intermediate in height?

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: pure tall (TT) × pure short (tt).

    ½ mark

  2. Gametes: the tall parent gives only T; the short parent gives only t.

    ½ mark

  3. F₁ progeny: T × t → Tt. All F₁ plants are tall (hybrid tall).

    1 mark

  4. Observation 1: all the F₁ plants were tall, so they resembled only one parent (the tall one).

    ½ mark

  5. Observation 2: no medium-height or short plants appeared in the F₁ generation. There was no blending; the trait for shortness was not expressed.

    ½ mark

Answer: TT (tall) × tt (short) → gametes T and t → F₁ all Tt; all F₁ plants were tall, with no medium or short plants (tallness is dominant).

Where the marks are

  • Writes the parents as TT × tt (½ mark)
  • Shows the gametes T and t (½ mark)
  • Shows the F₁ genotype Tt as all tall (1 mark)
  • Any two observations: all plants tall / resemble one parent / no medium or short plants (½ + ½ marks)

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 31/3/1: 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.