Undergone regulatory process: No

SDN Types

Classification of GnEd categories relevant to regulatory considerations

Friedrichs et al. (2019) An overview of regulatory approaches to genome editing in agriculture. Biotechnology Research and Innovation, 3(2), pp.208-220 defined three principal categories of GnEd which have a direct bearing on regulatory considerations: site-directed nuclease (SDN) SDN-1, SDN-2 and SDN-3:

SDN-1 involves the unguided repair of a specific DSB by NHEJ. Spontaneous repair of this break may result in a mutation that modifies a gene's activity, or causes gene silencing or KO. Efficient method, with many applications already.

SDN-2 involves a nucleic acid sequence donor, usually short single-stranded DNA, to direct the repair of a specific double strand break (DSB). The donor is identified as a repair template, enabling the insertion of the mutation(s) at the target site, because it carries one or more minor mutations surrounded by two homology sequences that match sequences either side of the DSB.

SDN-3 involves a sequence donor, usually double-stranded DNA carrying a gene or an even longer genetic element, to direct the repair of a targeted DSB. Given that the donor's two ends are homologous to the DSB ends (often more than 800 bp each), the donor can be introduced at the target site as a repair template since it is recognized by the DSB ends.

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