Sure it matters. They say that "all mutations cluster around the Cas9 cleavage site at position −3, suggesting that the escape mutations were generated in the p

Sure it matters. They say that "all mutations cluster around the Cas9 cleavage site at position −3, suggesting that the escape mutations were generated in the process of HIV-1 inhibition." http://www.ncbi.nlm.nih.gov/pubmed/26796669 http://www.ncbi.nlm.nih.gov/pubmed/26796669 Perhaps instead the virus that infected some cells that was already mutated, so it was resistant to the cleavage (due to lacking the recognition site). These are totally different mechanisms.