Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)

 by Annika Bright

Although gene editing technology had been discovered previously to 2012, Clustered Regularly Interspaced Short Palindromic Repeats - or simply, CRISPR, is a new-found method of gene editing technology that has allowed scientists to use it to control and modify DNA, including viral DNA. 

This CRISPR technology was initially a naturally occurring process within bacterial immune systems. In bacterial immune systems, it is known to protect both archaea and bacteria against viral invasion and ultimately destruction. CRISPR/Cas9 is characterised by two individual components which include a guide RNA - to identify the sequence of DNA that needs to be edited and the Cas9 protein - which is able to slice DNA in order to modify it. Within the context of the bacterium, as the viral DNA enters, the Cas proteins cut through a section of viral DNA and place this within the bacterium’s CRISPR. The embedded viral DNA is then copied and replicated into RNA which attaches onto the Cas9 protein. Once another identical piece of viral DNA re-enters the bacterium, this Cas9 protein is able to detect its genetic code and therefore slices through it, making it unable to affect the bacterium. Within genetic engineering in plants for example, once a cut has been made in the DNA using the Cas9 protein, nonhomologous end joining occurs and joins ends together. However, due to gaps between the bases, the gene created by this end joining may not always be usable and so, by using a DNA template in combination with CRISPR, an alternative process - homology directed repair can take place which allows for a much more accurate repair. Thus, many scientists have suggested that this genetic tool may aid in single gene diseases such as Sickle cell disease - by modifying the affected gene, in this case, the HBB gene.

Unsurprisingly, this technique has the ability to revolutionise genetic engineering within the medical field, but also, within a diverse range of organisms. In 2015, the regeneration of muscle tissue within mice was one of the first experimental successes that was achieved through this technique. The mice used within the experiment had the condition, Duchenne muscular dystrophy which results in detrimental symptoms such as the degeneration and weakening of muscles. Thus, the benefits of CRISPR have illustrated its promising nature.