CRISPR-Cas9 Gene Editing
Cas9 is a protein that cuts DNA, and a guide RNA tells it where. When the guide pairs with a matching sequence, Cas9 cuts both strands, and the cell's own repair machinery then fixes the break, which can switch off a gene or let a new sequence be added.
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Labelled parts
Key points
- The guide RNA gives specificity: about 20 bases pair with the target DNA.
- Cas9 cuts next to a short sequence called a PAM, using magnesium ions in its nuclease domains.
- The outcome depends on how the cell repairs the break.
Check yourself
What guides Cas9 to the right place in the genome?
Check yourself
What happens after Cas9 cuts the DNA?