CRISPR-Cas9 Genome Editing, in simple words, is a technique using which scientists can change an organism’s DNA. Recently, on 7th October 2020, the Royal Swedish Academy of Sciences has awarded the Nobel Prize in Chemistry for 2020 to Jennifer A. Doudna and Emmanuelle Charpentier for the development of CRISPR-Cas9 genetic scissors.
The Advent of Genetic Engineering
Genetic Engineering refers to the alteration of an organism’s DNA to change its characteristics (phenotype) in the desired manner. This technique uses biotechnology and is employed in the field of molecular biology. Genetic engineering is used in making genetically modified crops and foods in order to add more nutritional value and to get a higher yield. Jack Williamson, an American science fiction writer, is credited for coining the term “genetic engineering” in his fiction based novel Dragon’s Island which was published in the year 1951. Before direct DNA manipulation, techniques like selective breeding, artificial selection, and mutation breeding were used for genome alteration. The problem with these methods is that these are subjected to unpredictable results. Also, these techniques are limited when it comes to inserting a specific gene or sequence within the genome. That is why the need for CRISPR-Cas9 Genome Editing arose.
Origin of CRISPER-Cas9 System
A Japanese scientist Yoshizumi Ishino with his team in the year 1980s discovered a cluster of identical repeats interspaced with non-identical segments called spacers in a bacteria. It was named CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) by Francisco Mojica and Ruud Jansen in 2001. A few independent groups of scientists then noticed that these clusters contain the sequence of DNA of the virus that had attacked them. This identified sequence of bacteria worked as an early warning system next time the virus invaded. Hence, all and all, the CRISPER segment was able to identify and detect the matching DNA sequence in the attacking viruses.
This is not only the CRISPER that saved the life of the bacteria from the invading virus, the other important thing is some special kind of enzyme that is called Cas9. This Cas9 enzyme also contained a copy of the matching DNA sequence, its function is to find the same DNA sequence and slice it to break it apart in order to destroy it completely.
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What is the CRISPR-Cas9 Genome Editing Technology?
Termed as CRISPR-Cas9 genetic scissors, this system is an advanced tool in the field of genetic engineering that can perform genome editing in a precise manner. In 2012, researchers and the Nobel laureates Jennifer Doudna and Emmanuelle Charpentier found that this technique can be explored and can be used to destroy and replace a specific genetic sequence by reprogramming the CRISPR associated protein 9 i.e., Cas9.
As we know that this system is made of two important parts 1) a single guide RNA (combining crRNA and tracrRNA) and 2) a nuclease protein such as Cas9. Using this complex system we can provide our choice of genetic information in the Cas9 that can replace naturally occurring CRISPER.
Cas9 performs a double-strand cut on the entire helix at the pre-determined point. When the cut is found in the DNA, it tries to repair it on its own but this can be error-prone and can turn the gene function off. The other way to get this right is to introduce a repair template which is nothing but a DNA molecule. This template consists of the new code that needs to be inserted in the DNA.
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Need for Regulation in Genome Editing
CRISPR-Cas9 Genome Editing technology is a breakthrough invention in biotechnology and medicine. On one hand, there are its positives that it can cure a person who is infected with genetically linked diseases, on the other hand, there are its bad effects also, like changing the human evolution pattern. The want of designer babies and its use in biological weaponry are some major concerns that can destroy the basis of human beings. Hence, strict regulation and control over the usage of genome editing is the need of the hour.