📌 Topic 03 of 6 · Chapter 04 · Biotechnology & Genetic Engineering
CRISPR-Cas9 Gene Editing Technology
How CRISPR works, applications, Nobel Prize 2020, ethical concerns — complete notes for UPSC & PSC exams.
✂️ CRISPR-Cas9 — What is it?
- CRISPR = Clustered Regularly Interspaced Short Palindromic Repeats
- Cas9 = CRISPR-associated protein 9 — acts as “molecular scissors” to cut DNA at specific locations
- Originally discovered as a bacterial immune system against viruses
- Adapted as a gene editing tool by Jennifer Doudna and Emmanuelle Charpentier (2012)
- Nobel Prize in Chemistry 2020 — Jennifer Doudna (USA) and Emmanuelle Charpentier (France)
✂️ How CRISPR-Cas9 Works
- Step 1: Design a “guide RNA” (gRNA) that matches the target DNA sequence
- Step 2: gRNA guides the Cas9 protein to the exact location in the genome
- Step 3: Cas9 cuts both strands of DNA at the target location
- Step 4: Cell’s natural repair mechanisms fix the cut — gene can be disabled, corrected, or new gene inserted
- Much more precise, cheaper, and faster than previous gene editing tools (TALEN, ZFN)
✂️ Applications of CRISPR
| Application | Details |
|---|---|
| Treating genetic diseases | Sickle cell disease, thalassemia, Huntington’s disease — first CRISPR therapy approved (2023) for sickle cell |
| Cancer therapy | Engineering immune cells (T-cells) to attack cancer |
| Disease-resistant crops | Developing crops resistant to diseases without introducing foreign genes |
| Gene drives | Spreading genetic changes through wild populations — e.g., eliminating malaria-carrying mosquitoes |
| Drug discovery | Creating disease models; identifying drug targets |
✂️ Ethical Concerns
- “Designer babies” — editing embryo genes for non-medical traits (intelligence, appearance)
- Germline editing — changes passed to future generations; irreversible
- Off-target effects — unintended cuts in wrong DNA locations
- He Jiankui controversy (2018) — Chinese scientist edited human embryos → twin girls born with edited CCR5 gene → global outrage; sentenced to prison
- Most countries ban germline editing for reproductive purposes
📌 Key Exam Points:
• CRISPR = Clustered Regularly Interspaced Short Palindromic Repeats
• Cas9 = “molecular scissors” = cuts DNA at specific location
• Nobel Prize Chemistry 2020 = Jennifer Doudna + Emmanuelle Charpentier
• First CRISPR therapy approved (2023) = sickle cell disease
• He Jiankui (2018) = first CRISPR babies = global controversy
• CRISPR = Clustered Regularly Interspaced Short Palindromic Repeats
• Cas9 = “molecular scissors” = cuts DNA at specific location
• Nobel Prize Chemistry 2020 = Jennifer Doudna + Emmanuelle Charpentier
• First CRISPR therapy approved (2023) = sickle cell disease
• He Jiankui (2018) = first CRISPR babies = global controversy