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In human beings, the… (Class 10 Science 2024, Q23b)

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ScienceCBSE Class 10 · Board exam 2024, set 31/3/1 · 2 marks · Very short answer

CBSE Class 10 Science 2024: question 23(b)

Set in the CBSE Class 10 board exam of 2024, paper 31/3/1, section B, question 23(b), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q23(b) · 2 marks · Very short answerHeredity

In human beings, the probability of getting a male or a female child is 50%. Explain with the help of a flow diagram only.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/3/1.

Hints

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

Hint 1

Write the sex chromosomes of the father and the mother.

Hint 2

How many types of sperm and how many types of egg are formed? Combine them.

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: Father XY × Mother XX.

    ½ mark

  2. Gametes: sperms are X or Y (two types, 50% each); eggs are all X.

    ½ mark

  3. Fertilisation: egg X + sperm X → XX (girl); egg X + sperm Y → XY (boy).

    ½ mark

  4. Offspring: XX : XY = 1 : 1, so the chance of a female child is 50% and of a male child is 50%. The sex of the child depends on which sperm fertilises the egg.

    ½ mark

Answer: XY × XX → gametes X, Y and X → XX (female, 50%) and XY (male, 50%)

Where the marks are

  • Parents shown as XY and XX (½ mark)
  • Gametes X and Y from father, X from mother (½ mark)
  • Combinations XX and XY shown (½ mark)
  • Concludes 50% female, 50% male (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 paper2024 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.