GENETIC SCISSORS

A Tool For Rewriting The Code Of Life

Jigisha Patnaik

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On 7th October,2020, the Royal Swedish Academy of Sciences decided to award the Nobel Prize in Chemistry to Emmanuelle Charpentier and Jennifer A Doudna for “the development of a method for genome editing”. They have unearthed one of the most terrific tools in the field of gene technology-- the CRISPR/Cas9 genetic scissors.

CRISPR-Cas9 is a technology using which the parts of a genome can be edited and modified, via adding, subtracting or altering the DNA sequence. This technology was adapted from the natural defence mechanisms of bacteria and single-celled organisms. These organisms use CRISPR derived RNA and various Cas proteins (including the Cas9 protein) to foil attacks by foreign viruses. This is a breakthrough innovation, in the field of genetics, because it has a lot of potential and can be used to treat a wide and variant range of medical conditions. It is also the most precise, cheap and versatile method of “gene editing” currently prevailing in our world.

CRISPR or Clustered Regularly Interspaced Short Palindromic Repeats is a family of DNA found in prokaryotic organisms. Whereas, Cas9 or CRISPR Associated protein 9 is a 160 kilodalton protein. It plays an important role in the immunological defence of certain bacteria. However, its main role is to cut DNA hence modify a cell’s genome. The CRISPR-Cas9 system consists of two key molecules, an enzyme (called Cas9) and a piece of RNA called guide RNA or gRNA, that mutate the DNA. The enzyme acts as a pair of molecular scissors which can cut the two strands of DNA at a particular location on the genome, from which bits of DNA can be added or removed. The gRNA consists of a small piece of pre-designed RNA sequence located within a longer RNA scaffold. The scaffold part binds to the DNA and the pre-designed sequence guides Cas9 to the right part of the genome, to make sure the enzyme (Cas9) cuts at the right point. The gRNA is designed to find and bind to a particular point in the DNA, which implies, the gRNA will only bind to the target sequence and no other parts of the genome. The Cas9 follows the gRNA and makes a cut across both the strands at that specific location. The cell recognises this cut and tries to repair it, hence mutation of the DNA occurs.

Over the years, there has been a lot of evolution in the field of genetics. There have been a lot of methods developed by scientists including “gene targeting”, which is quite valuable for gene studying, but it’s quite expensive and takes a long period of time to mutate the DNA. There are some other methods too, like CRISPR-Cas systems, transcription activator-like effector nucleases (TALENs) and zinc-finger nucleases. However, for the present time, we can say that CRISPR-Cas9 seems to be the most reliable method from every possible aspect. It has a lot of applications and implications. Although, the mutation of somatic cells has already been used to treat human disease in some exceptional and life-threatening cases, it can also cure a huge number of medical conditions which have a genetic component. Most of the applications of it are related to the mutation of somatic cells, but there has been a lot of interest in and debate of mutating germline cells. Because any change in the germline cells will be passed on from generations and has ethical implications.

Such an innovation is exemplary and can be the beginning to a lot more, in the forthcoming future of mankind. They not only change our future, but raise questions on the evolution of us. In a few years, it’s been expected that this method would be used more frequently and in large masses to cure diseases. There’s also been debates, whether it could be used to create “super humans”, and if it happens, Will it be ethically used? Would there be no more flaws and imperfections existing in humans of the future? Well, it’s for all of us to see. This innovation has unleashed the innumerable possibilities in the arena of genetics that can create the upheaval in biotechnology and medical science. Nevertheless, the extent of revolution in the field of genetic engineering still remain unpredictable yet intriguing!