By Catherine Qiu
Introducing CRISPR
Clustered Regularly Interspaced Palindromic Repeats (CRISPR), named after how its genes appear in bacterial immune systems, is a simple and revolutionary gene targeting tool.
Journey Through the Genome
A cellular apoptosis susceptibility (Cas) protein carries a guide RNA strand and also sometimes a new DNA strand. Together, the three of them scour a genome for a specific, desired target. Once the guide RNA finds its complementary proto spacer-adjacent motif (PAM) site in the genome, the Cas protein’s helicase or “scissors” make a cut.
Altering the Genome
Sometimes a new DNA strand is inserted where the DNA’s cut; other times, no new strand is inserted, leaving the DNA to mend itself through non-homologous end joining (NHEJ) or homology-directed repair (HDR).
According to the central dogma of molecular biology, this deliberate change to the DNA may alter the mRNA, which may alter the protein function and structure.
CRISPR Innovations
The description above describes CRISPR-Cas9 editing a DNA strand. Beyond CRISPR-Cas9, new CRISPR types are found in other bacterial and archaeal strains. Just as customers seek better features in new phone models, researchers seek faster, more accurate, and more innovative abilities in new CRISPR types (Vidyasagar).
For example, CRISPR-Cas13 can target RNA instead of DNA. CRISPR-Cas13 could help cut up viral RNA and detect RNA viral infections, such as COVID-19 (“Enabling Coronavirus Detection”). Additionally, in a technique called base editing, a catalytically deactivated Cas protein is attached to another enzyme. The additional enzyme chemically alters one DNA base at a time, making no drastic cuts (Begley).
A Note on the Future of Gene Editing
Even though CRISPR is currently still in its early stages, it is clear to see that CRISPR has potential. It is easier to use and cheaper than other gene-editing options. Many ethical questions still need to be debated upon and new policies enacted shortly (Vidyasagar).
Learn more about CRISPR
To continue learning about CRISPR, I would recommend first checking out Bozeman's "What is CRISPR" video and WIRED’s “Biologist Explains One Concept in 5 Levels of Difficulty - CRISPR.”
Works Cited
Begley, Sharon. “Scientist David Liu Takes Your Questions on CRISPR and Prime Editing.” STAT, 6 Nov. 2019, www.statnews.com/2019/11/06/questions-david-liu-crispr-prime-editing-answers/.
“Enabling Coronavirus Detection Using CRISPR-Cas13: An Open-Access SHERLOCK Research Protocol.” MIT McGovern Institute, 23 Mar. 2020, mcgovern.mit.edu/2020/02/14/enabling-coronavirus-detection-using-crispr-cas13-an-open-access-sherlock-research-protocol/.
Vidyasagar, Aparna. “What Is CRISPR?” LiveScience, Purch, 21 Apr. 2018, www.livescience.com/58790-crispr-explained.html.
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