What is Cas9 protein that is often mentioned in news?
Answer & explanation
Answer: (a) A molecular scissors used in targeted gene editing
Cas9 is an enzyme that cuts DNA at a spot chosen by a guide RNA, which is why it is called molecular scissors. It is the cutting tool of CRISPR-Cas9 gene editing.
- ✓ (a) The guide RNA carries the address of the target DNA and Cas9 makes the cut there. Once the DNA is cut, the cell's repair process can be used to change the gene.
- ✗ (b) Cas9 is a cutting enzyme, not a sensor. Some diagnostic tests borrow it, but the protein itself is not a biosensor.
- ✗ (c) Cas9 is a protein (an enzyme), not a gene. It can be used to edit genes, including those that help plants resist pests, but it is not that gene.
Remember · CRISPR-Cas9: a guide RNA finds the DNA address and the Cas9 enzyme, the 'molecular scissors', cuts it.
Sources
- PIB, Ministry of Science & Technology: CRISPR gene-editing possible in temperature sensitive organisms, plants & crop varieties (3 Nov 2022) ↗ “the associated Cas9 enzyme, which acts as molecular scissors to cut DNA at a location specified by a guide RNA, can bind to and cut the target DNA at very low temperatures.”
Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·