Select the correct statement/s with respect to mechanism of sex determination in Grasshopper. A. It is an example of female heterogamety. B. Male produces two different types of gametes either with or without X chromosome. C. Total number of chromosomes (autosomes and sex chromosomes) is same in both males and females. D. All eggs bear an additional X chromosome besides the autosomes. Choose the correct answer from the options given below:
Answer: (C) (B) and (D) only. Answer: (C) (B) and (D) only Solution: In the grasshopper (XO type, male heterogamety), statement B is correct: the male produces two types of gametes, with or without the X chromosome.
- A.(A) only
- B.(A) and (C) only
- C.(B) and (D) only✓
- D.(A), (C) and (D) only
Correct Answer
(C) (B) and (D) only
Solution & Explanation
Answer: (C) (B) and (D) only Solution: In the grasshopper (XO type, male heterogamety), statement B is correct: the male produces two types of gametes, with or without the X chromosome. Statement D is correct: all eggs bear an additional X chromosome besides the autosomes. Statement A is wrong (it is MALE heterogamety, not female). Statement C is wrong: the total chromosome number is NOT the same in both sexes (males have one X, females have two X, so males have one fewer chromosome). Hence only B and D are correct, option (3). NOTE: this contradicts the supplied key letter 'B' (option text '(A) and (C) only'), which states the two false statements; option (3) is the NCERT-correct answer. NCERT Reference: NCERT Class XII, Ch 4, p.70, lines 5-12 and 27-31: "the mechanism of sex determination is of the XO type, i.e., all eggs bear an additional X-chromosome besides the other chromosomes (autosomes). On the other hand, some of the sperms bear the X-chromosome whereas some do not ... Grasshopper is an example of XO type of sex determination in which the males have only one X-chromosome besides the autosomes, whereas females have a pair of X-chromosomes."