CRISPR-Cas9 is a revolutionary gene-editing technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding, or altering sections of the DNA sequence. The system consists of two key molecules. The first is an enzyme called Cas9, which acts as a pair of "molecular scissors" that can cut the two strands of DNA at a specific location in the genome. The second is a piece of RNA called guide RNA (gRNA), which is designed to find and bind to a specific sequence of DNA. The gRNA guides the Cas9 enzyme to the right part of the genome, ensuring that the cut is made at the correct location.
The technology was adapted from a naturally occurring genome editing system in bacteria and archaea. These organisms use CRISPR-derived RNA and various Cas proteins, including Cas9, to defend against invading viruses. The potential for harnessing this system for programmable genome editing was first demonstrated in 2012 by Emmanuelle Charpentier and Jennifer Doudna, who showed that the Cas9 enzyme could be programmed with a single guide RNA to cut any DNA sequence. This discovery, which earned them the 2020 Nobel Prize in Chemistry, transformed the system into a powerful and widely accessible gene-editing tool.
CRISPR-Cas9 has revolutionized the field of genetic engineering due to its simplicity, affordability, and high accuracy compared to previous techniques. It has a wide range of potential applications, including correcting genetic defects, treating and preventing the spread of diseases, and improving the resilience and yield of crops. It is a fundamental tool in biological research for studying gene function and has accelerated the discovery of new drugs and therapies. While its potential is vast, the technology has also sparked significant ethical debates, particularly concerning its use in human germline editing.