ScienceCBSE Class 10 · Board exam 2023, set 31/6/1 · 1 mark · MCQ

CBSE Class 10 Science 2023: question 9

Set in the CBSE Class 10 board exam of 2023, paper 31/6/1, section A, question 9, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q9 · 1 mark · MCQHeredity

In an experiment with pea plants, a pure tall plant (TT) is crossed with a pure short plant (tt). The ratio of pure tall plant to pure short plants in $F_{2}$ generation will be

(A)1 : 3
(B)3 : 1
(C)1 : 1
(D)2 : 1

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/6/1.

Hints

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

Hint 1

Write the genotype of the F1 plants first.

Hint 2

"Pure" means homozygous, so ignore the Tt plants.

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.

The $F_{1}$ plants are all $T t$ . Selfing them, $T t \times T t$ , gives $T T : T t : tt = 1 : 2 : 1$ in $F_{2}$ .
½ mark
Pure tall ( $T T$ ) to pure short ( $tt$ ) is therefore $1 : 1$ . Hence the answer is option (C).
½ mark

Answer: 1 : 1, option (C)

Where the marks are

F2 genotypic ratio 1:2:1, so TT : tt = 1 : 1 (1 mark)

Revise the chapter

Chapter: Heredity (notes, formulas, where marks are lost and every past question)
Topic: Mendel's Experiments and Monohybrid Cross

Practise this chapterBoard-style questions from Heredity, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 31/6/1: 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.

CBSE Class 10 Science 2023: question 9

Hints

Step-by-step solution

Revise the chapter

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