This article aims to answer three questions: what is CRISPR, how was it discovered, and why do we care?
What is CRISPR?
CRISPR is a scientific breakthrough in the biochemical field regarding precise and efficient genetic engineering. It’s an acronym for “Clustered Regularly Interspaced Short Palindromic Repeats”, which is essentially a mechanism that consists of the integration of small components of viral DNA into the prokaryotic organism’s genome, then using that genetic information to produce an RNA copy of sequences for detection and cleavage of future invading viruses.
This process of genome editing enables scientists to disable gene function entirely, make specific edits to the genome, and activate or inhibit gene expression, but the fundamental method consists of introducing two molecules into a target cell, a Cas-9 enzyme that makes precise and efficient cuts in the DNA, and a programmable single-guide RNA molecule forming a complex with genomic DNA, then locating and binding to a common 20-base sequence in the genome, near a three-nucleotide base called PAM (protospacer adjacent motif), resulting in breaks of the double helix in two endonuclease domains at the targeted active sites of the genome. It’s much easier to visualize, which can be done through this website: CRISPR-Cas9: Mechanism & Applications
How was it discovered?
This gene-editing tool was co-discovered by 2020 chemistry Nobel laureates Dr. Emmanuelle Charpentier and Jennifer Doudna, by curiously studying a bacteria’s microbial immune system, which protects it from viral infection.
As shown in the image above, the CRISPR bacterial immune response is defined by three stages: acquisition, biogenesis, and interference. Recognizing foreign DNA, acquiring the new viral genetic information, making a copy in the form of an RNA molecule, and proceeding with the cleavage using the Cas9 and RNA complex, causing a double-stranded helix disruption and leading to degradation of viral DNA in bacteria, since prokaryotic cells do not have robust DNA repair systems compared to eukaryotes who have sophisticated machines to repair these breaks either by introducing minor changes to the site or by incorporating a new piece of DNA.
Why should we care?
Put simply, this could hopefully mean a potential cure for cancerous and genetic diseases, agricultural products that adapt better to changing climate, as well as further research in almost every field. Besides an enormous controversy regarding ethical and social questions that are raised, it’s one small cut for man, but a giant leap for humanity.
Sources:
Sid Mukherjee and Jennifer Doudna Interview: https://www.youtube.com/watch?v=4fjwj92UNn4&t=3342s
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