Genome editing

The different generations of restriction endonucleases used for genome editing and the DNA repair pathways used to modify target DNA.

Genome editing, or genome engineering, or gene editing, is a type of genetic engineering in which DNA is inserted, deleted, modified or replaced in the genome of a living organism. Unlike early genetic engineering techniques that randomly insert genetic material into a host genome, genome editing targets the insertions to site-specific locations.

Programmable molecules called restriction endonucleases, also known as gene editors or molecular scissors, are used to create double-strand breaks (DSBs) at desired locations in the genome. The induced breaks are repaired through homology-directed recombination (HDR) or non-homologous end joining (NHEJ), resulting in targeted mutations.

The development of CRISPR gene editing in 2015 improved the efficiency, specificity, and practicality of large-scale genome editing.

One of the earliest and most efficient methods of geonome editing is base editing. It does not require breaking and recombining the genomic DNA strands, and thus avoids the random insertions and deletions associated with these procedures. However, it is only appropriate for precise editing of single nucleotides. It employs nucleobase modifying enzymes directed by nucleic acid guide sequences. It was first described in the 1990s and has seen a resurgence more recently.

Since 2015, genome editing has been experimentally investigated on non-viable human embryos. In 2019, the first humans were born from genome-edited embryos using the CRISPR technique, as a result of the controversial He Jiankui affair.