CRISPR-Cas is a new technology for editing the genome in situ in cells. It works through an enzyme that splices out a target small fragment of DNA and replaces it with the complementary sequence of another nucleic acid fragment called a guide RNA. The guide RNA can be designed by hand and supplied exogenously. It contains both the targeting sequence and the replacement sequence, allowing a scientist to essentially decide exactly what DNA should be replaced and with what other DNA sequence.
To those unfamiliar with DNA sequences and their composite blocks call nucleotides, it may not be obvious that the choice of the targeting sequence is critical. Some sequences occur by random chance in many places throughout the genome, others can be complex and highly specific and potentially occur only once (usually be being longer). The genome is so large, it is often not possible to assess it completely for a guide sequence, so scientists have always suspected that any attempt at CRISPR-Cas will result in unexpected changes at unpredictable places elsewhere in the genome. The spectre of these off-targets has tempered expectations about the use of CRISPR-Cas.
Now, researchers have shown that they could develop a tool to make this off-target assessment. Basically, for any given guide RNA sequence, the system appears to accurately predict the extent of off-target activity. Importantly, this means it may be used to find guide RNA sequences that are unique, which they claim to have accomplished. Thus, for at least the desired edits that pass their test, CRISPR-Cas should be safe, and off-targets should be eliminated, a goal of GeneCentrix’ algorithms as well.