A word processor lets you jump to an exact word and swap it. CRISPR gives biologists that find-and-replace power on DNA — guiding molecular scissors to one precise spot in a genome to cut and edit a single gene.
Programmable editing of the genome
CRISPR-Cas9 lets scientists edit DNA at a chosen location. A short guide RNA is designed to match a target sequence; it leads the Cas9 enzyme there, which cuts both strands. The cell's repair machinery then either disables the gene or, given a template, pastes in a new sequence.
The specificity comes from the guide RNA's base-pairing with the target DNA. Change the guide's sequence and you retarget the whole system — which is what makes CRISPR so flexible.
CRISPR is being used to develop therapies for sickle-cell disease and to engineer disease-resistant crops.
Editing somatic cells affects one patient; editing germline (embryos, eggs, sperm) changes all future descendants and raises serious ethical questions the field treats with great caution.
- You want Cas9 to cut a different gene.
- Identify which component determines where it cuts.
- State what you would change.
What you should see: The guide RNA determines the target, so you redesign the guide RNA to match the new gene's sequence.