CRISPR/Cas9: Nature's gift to prokaryotes and an auspicious tool in genome editing

Clustered regularly interspaced short palindromic repeats (CRISPR) is a family of DNA direct repeats found in many prokaryotic genomes. It was discovered in bacteria as their (adaptive) immune system against invading viruses. Cas9 is an endonuclease enzyme linked with the CRISPR system in bacteria. Bacteria use the Cas9 enzyme to chop viral DNA sequences by unwinding it and then finding the complementary base pairs to the guide RNA. CRISPR/Cas9 is a modern and powerful molecular biology approach that is widely used in genome engineering (to activate/repress gene expression). It can be used in vivo to cause targeted genome modifications with better efficiency as compared to meganucleases, zinc- fi nger nucleases and transcription activator-like effector nucleases. CRISPR/Cas9 is a simple, reliable, and rapid method for causing gene alterations that open new horizons of gene editing in a variety of living organisms, including humans, for the treatment of several diseases. In this short review, we explored the basic mechanisms underlying its working principles along with some of its current applications in a number of diverse fields.