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Sex determination in human beings

Usually 1 marks a paper · mostly MCQs and assertion-reason · asked in 2 of the last papers

Notes are being written

The board questions below are real and complete — they come from the CBSE papers themselves. The written notes for this topic are still being prepared.

Board questions on this topic

6 from the CBSE papers we hold — the exact wording the board used.

2024MCQ·1 mark·Q8

Consider the following statements: (i) The sex of a child is determined by what it inherits from the mother. (ii) The sex of a child is determined by what it inherits from the father. (iii) The probability of having a male child is more than that of a female child. (iv) The sex of a child is determined at the time of fertilisation when male and female gametes fuse to form a zygote. The correct statements are:

  1. (a) (i) and (iii)
  2. (b) (ii) and (iv)
  3. (c) (iii) and (iv)
  4. (d) (i), (iii) and (iv)

2023Assertion-Reason·1 mark·Q18

Assertion (A): Genes inherited from the parents decide the sex of a child. Reason (R): X chromosome in a male child is inherited from his father. Options:

  1. (a) Both
  2. (b) and (R) are true and (R) is the correct explanation of (A).
  3. (c) Both
  4. (d) and (R) are true, but (R) is not the correct explanation of (A).
  5. (e) is true, but (R) is false.
  6. (f) is false, but (R) is true.

2022Case based·1 mark·Q14(a)

Sex-determination in humans: humans have 46 (23 pairs) chromosomes; 44 (22 pairs) control body characters and 2 (one pair) are sex chromosomes of two types - X chromosome and Y chromosome; at fertilisation the type of male gamete that fuses with the female gamete decides the sex of the newborn. Why is a pair of sex chromosomes in human beings called a mismatched pair in terms of type and size?

2022Case based·1 mark·Q14(b)

Sex-determination in humans (46 chromosomes: 44 autosomes + 2 sex chromosomes X and Y; sex of newborn decided by which male gamete fuses with the female gamete). Out of male or female, which of them has a perfect pair of sex chromosomes? In case of a perfect pair, will the gametes produced be of the same kind or of a different kind?

2022Case based·2 marks·Q14(c)(i)

Sex-determination in humans (46 chromosomes: 44 autosomes + 2 sex chromosomes X and Y; sex of newborn decided by which male gamete fuses with the female gamete). Write the names of two organisms whose sex determination is not done on a genetic basis. Explain the process of their sex determination.

2022Case based·2 marks·Q14(c)(ii)

Sex-determination in humans (46 chromosomes: 44 autosomes + 2 sex chromosomes X and Y; sex of newborn decided by which male gamete fuses with the female gamete). With the help of a flow chart only, show how sex determination in human beings takes place genetically.