UPSC Prelims 2001 · General Studies

Question 129: Science and Technology

Which of the following features of DNA makes it uniquely suited to store and transmit genetic information from generation to generation?

aComplementarity of the two strands

bDouble helix

cNumber of base pairs per turn

dSugar phosphate backbone

AnswerThe answer is (a).

Complementarity of the two strands (A pairs with T, G with C) is what suits DNA to storing and passing on genetic information: each strand carries the information needed to rebuild the other, so DNA can be copied faithfully when cells divide. The double helix, base pairs per turn and sugar-phosphate backbone give DNA its shape and stability but do not by themselves supply a copying mechanism. Remember that complementarity makes replication possible.

Why each option is right or wrong

(a) Right: complementarity allows faithful copying.
(b) The double helix gives structure but not the copying mechanism.
(c) The number of base pairs per turn is a structural detail.
(d) The backbone gives stability, not information.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2001, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.