๐ Topic 03 of 6 ยท Chapter 04 ยท Biotechnology & Genetic Engineering
CRISPR-Cas9 Gene Editing Technology
How CRISPR works, applications, Nobel Prize 2020, ethical concerns โ complete notes for UPSC & PSC exams.
โ๏ธ CRISPR-Cas9 โ What is it?
- CRISPR = Clustered Regularly Interspaced Short Palindromic Repeats
- Cas9 = CRISPR-associated protein 9 โ 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 โ Jennifer Doudna (USA) and Emmanuelle Charpentier (France)
โ๏ธ 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 โ gene can be disabled, corrected, or new gene inserted
- Much more precise, cheaper, and faster than previous gene editing tools (TALEN, ZFN)
โ๏ธ Applications of CRISPR
| Application | Details |
|---|---|
| Treating genetic diseases | Sickle cell disease, thalassemia, Huntington’s disease โ 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 โ e.g., eliminating malaria-carrying mosquitoes |
| Drug discovery | Creating disease models; identifying drug targets |
โ๏ธ Ethical Concerns
- “Designer babies” โ editing embryo genes for non-medical traits (intelligence, appearance)
- Germline editing โ changes passed to future generations; irreversible
- Off-target effects โ unintended cuts in wrong DNA locations
- He Jiankui controversy (2018) โ Chinese scientist edited human embryos โ twin girls born with edited CCR5 gene โ global outrage; sentenced to prison
- Most countries ban germline editing for reproductive purposes
๐ Key Exam Points:
โข CRISPR = Clustered Regularly Interspaced Short Palindromic Repeats
โข Cas9 = “molecular scissors” = cuts DNA at specific location
โข Nobel Prize Chemistry 2020 = Jennifer Doudna + Emmanuelle Charpentier
โข First CRISPR therapy approved (2023) = sickle cell disease
โข He Jiankui (2018) = first CRISPR babies = global controversy
โข CRISPR = Clustered Regularly Interspaced Short Palindromic Repeats
โข Cas9 = “molecular scissors” = cuts DNA at specific location
โข Nobel Prize Chemistry 2020 = Jennifer Doudna + Emmanuelle Charpentier
โข First CRISPR therapy approved (2023) = sickle cell disease
โข He Jiankui (2018) = first CRISPR babies = global controversy