CRISPR-Cas9: The next best thing?

Written by Ivory Chen

A large part of the reason why genetic editing has experienced so much evolution within the past 20 years is due to the development of the RNP (ribonucleic protein) known as CRISPR-Cas 9. First invented in 1987, CRISPR has revolutionized the study of genetics. Prior to the use of CRISPR, RNPs known as ZFNs and TALENs were utilized. However, the lack of accuracy, efficiency, and overall success made CRISPR an increasingly sought after alternative.

At a basic level, the CRISPR-Cas 9 system involves three main components: a PAM site, gRNA strand, and a cutting mechanism. The purpose of the system is to edit specific points of a DNA in a cell to potentially fix mutations. In order to correctly identify the location of a mutation, scientists craft a gRNA strand, or guiding RNA. This strand is complementary to the strand of DNA where the mutation is located, and “binds” to the gene, allowing the Cas 9 system to create a double-strand controlled cut. The system binds at what is known as a PAM site, or any location near the site of the mutation that follows the pattern of 5’ N-G-G 3’. The first nucleotide “N” can be any nucleotide.

The purpose of creating a double-strand controlled cut at the site of the mutation is for the cell to naturally undergo NHEJ repair, a naturally occurring process by the cell, hopefully fixing the mutation.

References

“What Is CRISPR?” The Jackson Laboratory, 

www.jax.org/personalized-medicine/precision-medicine-and-you/what-is-crispr. Accessed 26 July 2024.