Summary
A guide RNA directs the Cas9 nuclease to a matching DNA site to cut it, enabling precise editing.
In depth
Cas9 binds a guide RNA (crRNA plus tracrRNA, or a fused sgRNA), scans DNA for a PAM motif (NGG) and unwinds the neighbouring target; two nuclease domains (HNH and RuvC) cut both strands 3 bp upstream of the PAM. The cell repairs the break by NHEJ (knockouts) or HDR with a template (precise edits).
Off-target cutting is a safety concern. Doudna and Charpentier received the 2020 Nobel Prize.
Frequently asked questions
What is CRISPR-Cas9 Mechanism?
A guide RNA directs the Cas9 nuclease to a matching DNA site to cut it, enabling precise editing.
Which area of biology covers CRISPR-Cas9 Mechanism, and how advanced is it?
CRISPR-Cas9 Mechanism is one of the 52 topics in Molecular Biology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Homologous Recombination, RNA Interference, Telomerase.
Can you give an example of CRISPR-Cas9 Mechanism?
The therapy exagamglogene (Casgevy) edits blood stem cells to treat sickle cell disease.
What should I learn before CRISPR-Cas9 Mechanism?
Work through the Beginner topics in Molecular Biology first, such as Central Dogma, DNA Replication, Base Pairing, then return to CRISPR-Cas9 Mechanism. Advanced topics assume the Intermediate vocabulary.
What topics are related to CRISPR-Cas9 Mechanism?
The closest topics to CRISPR-Cas9 Mechanism are Homologous Recombination, RNA Interference, Telomerase, Lac Operon. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand CRISPR-Cas9 Mechanism?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for CRISPR-Cas9 Mechanism. To practise the whole of Molecular Biology, use the Molecular Biology quiz.
How is CRISPR-Cas9 Mechanism different from Homologous Recombination?
CRISPR-Cas9 Mechanism: A guide RNA directs the Cas9 nuclease to a matching DNA site to cut it, enabling precise editing. Homologous Recombination: An accurate repair pathway and meiotic mechanism exchanging DNA between similar sequences using RAD51. Read both side by side and note what each one explains.
How should I study CRISPR-Cas9 Mechanism step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Homologous Recombination and explain the difference aloud. Finally, take the Molecular Biology quiz and come back to this page for any question you miss.