UPSC Prelims 2022 · GS Paper I
Question 99: Science and Technology
Consider the following statements : DNA Barcoding can be a tool to :
- 1.assess the age of a plant or animal.
- 2.distinguish among species that look alike.
- 3.identify undesirable animal or plant materials in processed foods.
Which of the statements given above is/are correct ?
AnswerUPSC’s answer is (d).
DNA barcoding identifies a species by reading a short, standard stretch of DNA, such as the COI gene in animals, and matching it against a reference library. That lets it distinguish look-alike species and detect unwanted plant or animal material in processed foods. It cannot tell an organism's age, so statement 1 is false.
- 1. A DNA barcode identifies species; it does not reveal age.
- 2. It can distinguish species that look alike.
- 3. It can detect undesirable plant or animal material in processed foods.
How you could have got this
- If you were sure statement 1 is not correct, (a) and (c) go: each of them includes 1.
What you needed to know: A DNA barcode identifies species; it does not reveal age.
- Then, if you were sure statement 2 is correct, (b) goes: it leaves 2 out.
What you needed to know: It can distinguish species that look alike.
Only (d) 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. Barcoding cannot give age.
- (b) Wrong. Statement 2 on look-alike species is also correct.
- (c) Wrong. Statement 1 is false.
- (d) Correct. It separates look-alike species and finds unwanted material in foods.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2022, General Studies Paper I, Series A. The paper on upsc.gov.in.