Gene Editing and CRISPR: Medical and Ethical Dimensions
TOPIC CLASSIFICATION
Subject: Science & Technology Sub-area: Biotechnology Prelim PYQ Trend: Moderate (concept questions, Nobel Prize related) Mains Relevance: GS-3 (Science & Technology, Ethics)
EXAMINER REASONING
CRISPR-Cas9 won the Nobel Prize in Chemistry (2020), making it a high-probability UPSC topic. The examiner tests: (a) technical understanding — how CRISPR works, components (Cas9, guide RNA, PAM sequence); (b) applications — gene therapy, agriculture (GM crops), disease models; (c) ethical dimensions — germline editing (He Jiankui case), designer babies, eugenics concerns; (d) regulatory framework in India — GEAC, DBT guidelines. Expect comparative questions with other gene-editing tools (ZFN, TALEN) and ethical dilemma questions.
Core Concept
What is Gene Editing? Gene editing is a type of genetic engineering in which DNA is inserted, deleted, modified, or replaced in the genome of a living organism using engineered nucleases (molecular scissors).
CRISPR-Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats):
- Discovery: Emmanuelle Charpentier and Jennifer Doudna (Nobel Prize 2020)
- Components: Cas9 enzyme (cuts DNA) + guide RNA (gRNA — targets specific DNA sequence) + PAM sequence (protospacer adjacent motif — required for cutting)
- How It Works: gRNA guides Cas9 to target DNA → Cas9 cuts both strands → cell's natural repair mechanisms (NHEJ or HDR) are used to modify the gene
- Advantages: Cheaper, faster, more precise than earlier methods (ZFN, TALEN)
Other Gene Editing Tools:
| Tool | Mechanism | Precision |
|---|---|---|
| ZFNs | Zinc finger proteins + FokI nuclease | Moderate |
| TALENs | TAL effector + FokI nuclease | High |
| CRISPR-Cas9 |