During DNA replication, DNA must be able to replicate itself to make two identical copies of the original DNA molecule. During this process, mistakes called mutations can occur. Some of these mutations are harmless because of the fidelity of the genetic code, and the nucleotide changes do not change the amino acids being coded for in the DNA sequence. Some other changes can have more noticeable effects. For example, sickle cell anemia is caused by a single nucleotide change that leads to a different amino acid to be coded for. What if there was a way to have an editing system go in and mix these mistakes? Well, researchers have been exploring the CRISPR-Cas9 system as a method to edit genomes. CRISPR stands for “clusters of regularly interspaced short palindromic repeats”, and Cas9 is an enzyme in the system that is able to cut DNA strands (https://www.livescience.com/58790-crispr-explained.html). The CRISPR system is a bacteria and archaea immune defense mechanism to protect their genomes from viruses. The region consists of palindromic repeats, meaning that the DNA strands read the same forward and backward, and spacers contain viral DNA. The spacers allow the organism to recognize the virus if it tries to infect them again. This is similar to how antibodies and vaccines create immunological memory in humans. The CRISPR DNA region is like a blueprint that encodes for RNAs that are able to carry out the editing process. The CRISPR RNAs, crRNA and tracrRNA, are able to pair with the Cas9 enzyme and guide Cas9 to target and cut parts of the virus’ DNA. Researchers have been able to figure out how CRISPR can become a gene-editing tool for organisms besides bacteria. They are able to create RNA that matches a unique DNA sequence in a particular gene that needs to be edited. From there, the RNA guides the Cas9 enzyme to cut the DNA. Afterward, the cell can repair the cut which introduced mutations that can turn off the gene or edit it. The CRISPR-Cas9 is a cheap, efficient, and accurate tool that can give a lot more insight into different functions of genes, diseases, and genetic therapies.
