Fig. 1

Nuclease-based genome editing creates a specific double-stranded break (DSB) in the genome and then allows the cell’s own endogenous repair machinery to repair the break. a When the editing of a single break occurs by nonhomologous end-joining (NHEJ), insertions/deletions are created at the site of the break. b When the editing of two DSBs occurs by NHEJ, chromosomal deletions, inversions or translocations can be created. c When editing of a single DSB occurs by homologous recombination (HR) using a provided donor sequence, precise changes in the nucleotide sequence ranging from a single base insertion to the introduction of a large cassette of genes can occur. Using NHEJ and HR mediated editing, it is now possible to inactivate genetic elements, create defined deletions ranging from a few bases to thousands of bases, and precise nucleotide changes to the sequence of the genome. AAV Adeno-associated virus, bps Basepairs, IDLV Integrase-deficient lentivirus