UPSC Prelims 2000 · General Studies

Question 127: Science and Technology

Assertion (A): In human beings, the females play a major role in determining the sex of the offspring. Reason (R): Women have two ‘X’ chromosomes.

aBoth A and R are true, and R is the correct explanation of A

bBoth A and R are true, but R is not a correct explanation of A

cA is true, but R is false

dA is false, but R is true

AnswerThe answer is (d).

The sex of a child is decided by the father. Every egg carries an X chromosome, while sperm carry either X or Y. An X sperm gives a girl (XX) and a Y sperm a boy (XY). So A is false, since women do not determine the sex of the child, though R is true, because women have two X chromosomes.

A. The father's sperm, carrying X or Y, decides the sex of the child.
R. Women have two X chromosomes.

How you could have got this

If you were sure statement 1 is not correct, only (d) is left: every other option says it is correct.

This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong

(a) A is false, so R cannot explain it.
(b) A is false, so this option is wrong.
(c) A is false, so this option is wrong.
(d) Right: A is false and R is true.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2000, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.