Table 2.

Ideal features for genome writing or editing platforms

Feature	Description
Simple	Only one custom biopolymer for each HDR or HR event
Multiplex	100% targeting at multiple sites, not merely ‘high efficiency’ at a single site
Robust	High efficiency in post-mitotic cells (e.g. neurons), broad sequence compatibility
Large regions	High efficiency of 10 kbp to 10 Mbp scale replacements, alternative strategies possible
Low toxicity	Low apoptosis, high specificity, genome integrity intact
Germline editing	Specific safeguards might include restriction to gametes and/or clonal analysis to reduce mosaicism
Reading and testing	Rapid feedback on many synthetic genomes via reporters, organoids and sequencing

HDR, homology-directed repair; HR, homologous recombination.