Before understanding what CRISPR is, and why it is so revolutionary, you first have to familiarize yourself with certain structures and mechanisms of all life as we know it.
DNA, Genes, and Genomes
An integral part of understanding what CRISPR is, is understanding the concepts of DNA, Genes, and the Genome. DNA (Deoxyribonucleic Acid) is a chemical code that is inherited from parent to offspring. The code is composed of four chemical bases, Adenine (A), Guanine (G), Cytosine (C) and Thymine (T). It carries with it is the “source code” from which all organisms are made.
A Gene is a collection of DNA that codes for a single protein. With each gene, carries a set of instructions that produce specific characteristics of an organism.
The Genome is what you call an organism’s complete set of genetic instructions. Everything from your height to the color of your eyes are dictated by your genes.
With that very brief intro of what genes and genomes are, the concept of gene editing, and finally CRISPR can be introduced. Gene editing is the deletion, insertion, or modification of the genome of an organism at a specific site.
And example of gene editing is The Golden Rice Project, where researchers were able to enhance the nutrient production in rice by introducing a gene sequence which coded for the production of a substance previously not produced by the rice.
What is CRISPR?
CRISPR was discovered in 1993 (one year after i was born), when scientist discovered repetitive palindromic segments of DNA interspaced with other fragments of genetic material in prokaryotes. They named the pieces of code Clustered Regularly Interspaced Short Palindromic Repeats, i.e CRISPR.
After studying CRISPR extensively, scientist figured out CRISPR was related to a self defense mechanism in bacteria synonymous with our mechanisms for immunity.
When bacteria and archaea encounter a viral infection, the prokaryotic cell employ a CRISPR-associated nuclease (CAS9) to precisely cut of a piece of viral DNA. This destroys the virus and the piece of foreign DNA (called a spacer) is stored between palindromic sequences of the CRISPR array, preserving the memory of a the infection. This way if the virus re-invades it can be quickly identified and destroyed.
The CRISPR system is composed to two parts, a guide RNA (gRNA) that is specific to the target DNA sequence and a non-specific CRISPR-associated endonuclease protein (Cas9), used for cutting.
After scientist figured out the mechanisms by which CRISPR operated, it did not take them long to figure out a way to utilize it to engineer the genome of virtually any organisms with great accuracy.