CRISPR system was discovered by a Japanese scientist. Naturally bacteria and many other prokaryotes have CRISPR system in their genome which they use as a self defense against a pathogen which is invading them. It consists of inter spaced, short palindromic nucleotide repeats which encode a guide RNA (gRNA). This guide RNA (gRNA) recognizes the target sequence on the pathogen. The gRNA is followed by Cas9 enzyme which along with the gRNA plays a very important role in breaking genome of the pathogen. Once the target gene is cut down the rest of the DNA can be rejoined by non homologous end joining.
But nowadays, scientists are using this system for genome editing and incorporating desired gene between the two ends which are cut down by CRISPR Cas9 system.
