View source for Prime Editing

'''Prime editing''' is a [[Genome Engineering|genome engineering]] technique that achieves precise DNA edits without requiring double-strand breaks or donor DNA templates. Developed by Andrew Anzalone and David Liu in 2019, it uses a catalytically impaired Cas9 nickase fused to a reverse transcriptase. A '''[[Guide RNA Design|prime editing guide RNA]]''' (pegRNA) both targets the edit and encodes the desired sequence change, which the reverse transcriptase writes directly into the genomic DNA at the nick site.

The system is effectively a '''molecular word processor''': it can perform all twelve types of point mutation, plus small insertions and deletions, with substantially fewer '''[[Off-Target Effects|off-target effects]]''' than conventional CRISPR. By avoiding double-strand breaks, prime editing sidesteps the cell's error-prone repair pathways — the primary source of unintended mutations in standard CRISPR editing.

However, prime editing is not universally applicable. It is most efficient for small edits (up to a few dozen base pairs). Larger insertions still require conventional homology-directed repair. And the delivery problem — getting the large prime editing machinery into target cells in vivo — remains a significant barrier to therapeutic application.

''Prime editing represents the culmination of a trend in genome engineering: the progressive replacement of biological processes with information processes. Where CRISPR recruited the cell's own repair machinery, prime editing replaces it entirely with a programmable molecular typewriter. The cell becomes a substrate; the editor becomes the author. Whether this is progress or hubris depends on how well we understand the substrate.''

[[Category:Technology]] [[Category:Biology]]