Skip to content

In a cross between… (Class 10 Science SQP 2025-26, Q5)

questionbuddy.in/q/cbse-10-science-2025-26-sqp-q5-cross-between-black-furred-rabbit

ScienceCBSE Class 10 · Sample paper, session 2025-26 · 1 mark · MCQ

CBSE Class 10 Science sample paper 2025-26: question 5

From the official CBSE sample question paper for 2025-26, section A, question 5, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q5 · 1 mark · MCQHeredity

In a cross between black furred rabbit (B) and white furred rabbit (b), all offspring were found to have black fur. What can be inferred about the genetic makeup of the parent rabbits?

  1. (A)
  2. (B)
  3. (C)
  4. (D)

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.

Hints

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

Hint 1

White fur appears only when the genotype is bb.

Hint 2

Check which cross can never give a bb offspring.

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. Black (B) is dominant over white (b). If even one parent were Bb, then crossing it with bb, or Bb with Bb, would give some white (bb) offspring.

  2. All offspring are black, so the black parent must be pure (BB) and the white parent is bb. Every offspring is then Bb, which is black. Answer: **(A) **.

    1 mark

Answer: Option (A): BB × bb

Where the marks are

  • Reasons that 100% black offspring means a homozygous dominant parent crossed with bb, option (A) (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 paperSample paper 2025-26: 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.