Targeted nucleases are genetic scissors that bind to specific DNA sequences, such as the CCR5 co-receptor, and create a DNA break there. The cell then attempts to repair that break, and that process can be used to precisely engineer a specific genetic outcome. Two protein-based nucleases, zinc fingers and TALENs, are commonly used for this technique. A newer technology, CRISPR, uses a complementary RNA sequence to achieve the same outcome.
The DNA break can be used in two ways: to knock out a specific gene or to use a type of genetic template called a homology donor in order to introduce a specific base pair change into the gene. That latter technique is called gene editing.
Credit: ktsimage for iStock via Thinkstock