2019 GS Paper I, all questions
UPSC Prelims 2019 · GS Paper I
Question 99: Science and Technology
What is Cas9 protein that is often mentioned in news?
aA molecular scissors used in targeted gene editing
bA biosensor used in the accurate detection of pathogens in patients
cA gene that makes plants pest-resistant
dA herbicidal substance synthesized in genetically modified crops
AnswerUPSC’s answer is (a).
Cas9 is an enzyme in the CRISPR-Cas9 gene-editing system. Guided by an RNA, it cuts DNA at a chosen site, which is why it is called molecular scissors, and the cell's repair then allows a gene to be disabled, corrected or added. It is not a biosensor, a pest-resistance gene or a herbicidal substance.
Why each option is right or wrong
- (a) Correct: Cas9 is the molecular scissors used in targeted gene editing.
- (b) Cas9 is not a biosensor for detecting pathogens.
- (c) Cas9 is an enzyme, not a pest-resistance gene.
- (d) Cas9 is not a herbicidal substance.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2019, General Studies Paper I, Series A. The paper on upsc.gov.in.