An Introduction to CRISPR: The Gene-Editing Breakthrough of Modern Biology

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We must have come across the article on the use of CRISPR technology for cutting out HIV-1 DNA from human immune cells. Let’s now take a look into the history and working of this technique…

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is a genome editing technology that allows precise modification of DNA in living organisms. It works like molecular scissors—cutting DNA at a specific location—and makes it possible to add, remove, or replace specific sequences.
It was originally discovered as a defense mechanism in E. coli against viruses (bacteriophages) by Yoshizumi Ishino in 1987. Bacteria store small pieces of viral DNA in their CRISPR sequences to “remember” past infections—just like our B cells remember viruses. If the same virus attacks again, Cas proteins (cutting enzymes like Cas9, Cas12, Cas13, etc.) use this stored information to recognize and disable the viral DNA. The guide RNA (gRNA) carries the sequence that matches the target DNA.

Step-by-step process:

1. gRNA is designed to match the gene that needs to be removed or replaced.


2. Cas9 protein and gRNA are introduced into the cell.


3. gRNA binds to the specific sequence, and Cas9 cuts at the precise location.


4. The cell then repairs the cut using either NHEJ or HDR (DNA repair mechanisms).
FACTS:

1. Its role as a bacterial immune mechanism was understood in the early 2000s, mainly by Francisco Mojica (Spain).


2. In 2012, Jennifer Doudna and Emmanuelle Charpentier demonstrated that CRISPR could be used as a programmable tool for gene editing.


3. They were awarded the Nobel Prize in Chemistry in 2020 for this discovery.


4. In 2018, a Chinese scientist used CRISPR on human embryos, raising serious ethical concerns.



This technology holds massive potential and is being applied in fields like gene therapy, cancer treatment, development of disease-resistant crops, and more.

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