UPSC Prelims 2012 · GS Paper I
Question 16: Science and Technology
With reference to 'stem cells', frequently in the news, which of the following statements is/are correct?
- 1.Stem cells can be derived from mammals only.
- 2.Stem cells can be used for screening new drugs.
- 3.Stem cells can be used for medical therapies.
Select the correct answer using the codes given below :
AnswerUPSC’s answer is (b).
Stem cells are unspecialised cells that can divide and turn into specialised cells. They are found in humans, other animals and plants (plant meristems), so they are not limited to mammals. They are used to screen new drugs on cultured cells and in medical therapies such as bone-marrow transplants and research on tissue repair.
- 1. Stem cells occur in other animals and in plants, not only in mammals.
- 2. Stem cell lines are used to test the effects of new drugs.
- 3. Stem cells underpin therapies such as bone-marrow transplants.
How you could have got this
- If you were sure statement 1 is not correct, (a) and (d) go: each of them includes 1.
What you needed to know: Stem cells occur in other animals and in plants, not only in mammals.
The red flag in statement 1 is “only”. In UPSC’s papers, statements with “only” were true 27% of the time (82 statements). A hint, not a rule.
- Then, if you were sure statement 2 is correct, (c) goes: it leaves 2 out.
What you needed to know: Stem cell lines are used to test the effects of new drugs.
Only (b) is left. You didn’t need statement 3.
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) Wrong: statement 1 is false because stem cells are not confined to mammals.
- (b) Correct: stem cells serve in drug screening and therapies; they are not limited to mammals.
- (c) Incomplete: stem cells are also used for drug screening.
- (d) Wrong: statement 1 is false, since stem cells also occur in other animals and plants.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2012, General Studies Paper I, Series A. The paper on upsc.gov.in.