Gene editing technology may be the fastest growing field of science in the 21st century. The invention of the CRISPR-Cas9 method started a revolution in gene editing because it is cheaper and more effective than previous methods. The founders won the 2020 Nobel Prize in Chemistry, yet there is much controversy over the ethical problems of genetic manipulation. C

RISPR-Cas in Nature.

DNA protection in prokaryotes
CRISPR (short palindromic repeats regularly arranged in groups) is a family of DNA systems in bacteria and archaea in the natural world. It plays an important role in the immune system of organisms. The mechanism is quite simple. CRISPR DNA fragments are taken from the genome (the complete set of genetic instructions of the organism. Each genome contains all the information needed to build that organism and enable its growth and development) of a bacteriophage virus that has infected it. The cell uses them to identify and destroy the bacteriophage if it tries to infect the organism again. Furthermore, bacteria can pass genes to each other, so that cells can pass information about the virus from one to the other.

The enzyme Cas9
Cas9 is an enzyme that uses CRISPR information as a notification. It uses sequence data to look for DNA fragments that “match” the CRISPR sequence. This means that CRISPR has a sequence that pairs with the DNA of the virus. When the two sequences “match,” we call them complementary.

The CRISPR-Cas9 system.
Finally, CRISPR and the Cas9 enzyme create a powerful immune system tool known as CRISPR-Cas9. It is widespread in bacteria – we can find it in more than half of all genomes and 90% of archaea genomes. It is the main cell defense system against bacteriophages, making it essential for bacterial life and evolution. How then is this mechanism used in gene editing?

Mechanism of genome editing using CRISPR
Molecular scissors.
CRISPR-Cas9 technology allows scientists to remove, alter or add sections of DNA. The Cas9 protein acts like molecular scissors. It cuts strands of DNA at a specific location, allowing changes to be made. Then a guide RNA (gRNA) consisting of a small piece of specially designed CRISPR RNA fragment in a more extended sequence. The longer part binds to the matrix DNA, while CRISPR guides Cas9 to the right place in the genome, just as it does in bacteria and archaea.

The CRISPR part is complementary to only one region of the genome, so it won’t bind anywhere else, which makes the technology precise. When Cas9 finds a complementary fragment, it cuts the DNA. The cell recognizes the cut as a lesion and repairs it by combining the mutation (a larger piece) with its DNA. The result is a functioning genome with a specific mutation.

Application of the CRISPR-Cas9 technology
DNA contains genes – detailed information about proteins and their creation. Genetic expression is when certain structures translate the information to create different molecules. Together, the information in the DNA and the factors that influence expression create us. DNA consists of information about each individual protein from which we are built–its structure, location, mode of expression, function, and more. Consequently, changing the DNA changes the body on a molecular level. This is what makes CRISPR-Cas9 such a powerful tool. Using the right sequences, we can change the way organisms live and tune them to suit our needs. Of course, there are problems related to which genes to use, where to put them, and how they will affect organisms.