Gene Editing (CRISPR-CAS9)
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Content
Introduction
- Gene editing is the process of genetic engineering in which DNA is inserted, deleted or replaced in the genome of an organism using engineered nucleases, or “molecular scissors”.
- These nuclease or enzymes create site-specific double strand breaks (DSBs) at desired locations
- The induced double strand breaks are repaired through end joining or recombination, resulting in targeted mutation.
What is (CRISPR-CAS9)
- CRISPR-CAS9 is a new genome editing tool, which is simpler, faster, cheaper, more versatile and more accurate than the previous techniques of editing DNA and has wide range of potential applications
- In popular usage, “CRISPR” (pronounced “crisper”) is shorthand for “CRISPR-Cas9”.
How does CRISPR-CAS9 work? (Clustered Regularly interspaced short palindromic repeats)
- The CRISPRs are specialized stretches of DNA.
- The CRISPR-CAS9 system consists of two key molecules that introduce a change into the DNA. These are:
- Enzyme called Cas9 (CRISPR associated Protein 9). This acts as pair of ‘molecular scissors’ that can cut two strands of DNA at a specific location in the genome so that bits of DNA can then be added or removed.
- A piece of RNA called guide RNA (gRNA). This consist of a small piece of pre-designated RNA sequence (20 bases long) located within the longer RNA scaffold. The scaffold part binds to DNA and pre-designated sequence ‘guides’ Cas9 to the right part of the genome. This makes sure that the Cas9 enzyme cuts at right point in genome.
Applications of CRISPR-CAS9
- The technology has had a revolutionary impact on life science.
- Its applications include correcting genetic defects, treating and preventing the spread of diseases like HIV, various cancers etc; and improving crops.
- For e.g. – In Feb 2020, it was used to modify the gene of three cancer patients to reprogram the immune system to fight off cancer cells, with no side effects so far.
- It has been used to eliminate HIV from infected cells and is being used to reverse congenital blindness.
- It has also been used in plants to develop resistance against pests and droughts.
Limitations
- Safety Concerns: Rouge Practices of Genetic Engineering have raised concerns. CRISPR is very simple to use and thus have made genetic editing very simple. For e.g. In Nov 2018, a scientist in China, He Jiankui used CRISPR on twin Embryos in China for enhancement of the qualities of baby. Scientific community considered this risky and unjustified and against the scientific and regulatory protocol.
- Further, we are not aware of knock-on effect of editing a gene would have.
- For one thing, it is known that modifying CCR5 to resist HIV could increase susceptibility to West Nile Virus.
- Ethics of CRISPR – Should humans be allowed to modify how the nature works?
Way Forward/ Conclusion
- The debate around the issue of gene editing on humans will continue for sometimes. What is important presently is that steps should be taken to enhance the regulation of the sector. If new experiments are being done, it should be done in a regulated environment without harming the safety of the participants.
- It is also vital that international community come together and formulate a framework as to what is acceptable in the field of human genetic modification, as work like this has serious implications in the spheres of global medical research, biomedical technology, and the human gene pool itself.
- Further, there should be a global consensus and strict regulation of preventing germline editing till all the future implications are not properly understood.
Example Questions
“Though genetic Engineering has been simplified by the Crisper-CaS9 technique, it has brought along with it a number of challenges” Elaborate [15 marks, 250 words]