This post was contributed by David Wyatt and Dale Ramsden, UNC at Chapel Hill.
One advantage to using the CRISPR/Cas system for genome engineering is the fact that Cas9 can be easily programmed to make a DNA double strand break (DSB) in the genome wherever the user chooses. After the initial cut, the next steps in the process involve repairing chromosomal DSBs. It is important to know that cells possess two major repair pathways – Non-Homologous End Joining (NHEJ) and Homology Directed Repair (HDR) – and how these pathways work, as this could be relevant when planning your experiment. This blog has previously considered the HDR pathway; below we’ll discuss NHEJ, and how it impacts what happens to Cas9-mediated DSBs in the genome.