UPSC Prelims 1999 · General Studies

Question 129: Science and Technology

Assertion (A): Insect-resistant transgenic cotton has been produced by inserting Bt gene. Reason (R): The Bt gene is derived from a bacterium.

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 (a).

Bt cotton carries a gene from the soil bacterium Bacillus thuringiensis, which makes a protein toxic to certain insect pests such as bollworms. So A is true and R is true. The given answer takes R as the explanation, since the gene taken from the bacterium gives the plant its insect resistance. Remember: Bt stands for Bacillus thuringiensis, the bacterial source of the gene.

A. Insect-resistant transgenic cotton was produced by inserting the Bt gene.
R. The Bt gene comes from a bacterium.

How you could have got this

If you were sure statement 1 is correct, (d) goes. Then judge the second statement; if it is correct too, decide whether it explains the first.

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) Right. Both are true; the bacterial gene is what makes the cotton insect-resistant.
(b) Wrong as given. The given answer treats R as the explanation of A.
(c) Wrong. R is true.
(d) Wrong. A is true.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 1999, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.