Britannica
Sources used in this answer
How do nucleases help scientists edit specific DNA sequences?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
gene editing
The CRISPR-Cas9 gene-editing complex from the bacterium Streptococcus pyogenes.
In the field of gene editing, nucleases act as molecular scissors that introduce precise, double-stranded breaks into DNA sequences. By creating these breaks at specific locations, scientists can trigger the cell’s natural repair mechanisms to remove existing DNA or insert replacement sequences, effectively correcting genetic mistakes.1
To achieve this precision, scientists use engineered systems that guide the nuclease to a target site:
- ZFNs and TALENs: These systems use custom-designed protein domains that bind to specific DNA sequences flanking a target site. Once bound, these domains bring together subunits of the nuclease Fok1, which then dimerizes to cut the DNA.1
- CRISPR-Cas9: This system utilizes RNA-DNA binding rather than protein-DNA binding. A "guide RNA" is designed to match a unique target sequence via base-pairing rules, directing the Cas9 nuclease to catalyze a cut at that exact location.12
These tools are essential for genetic engineering, allowing for highly specific modifications that hold significant potential for treating human disease, though they also raise profound ethical questions regarding the morality of altering human genetics.12