CRISPR-Cas9 gene editing – find, cut and repair
BiologyBiotechnologyAges 17–18
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Biotechnology
A textbook-style model of gene editing. Load one of four guide RNAs into Cas9 and watch it search made-up DNA: it opens the DNA only next to a PAM and cuts both strands where the guide pairs fully. Test each guide in 100 cells to spot off-target cuts. Then follow how the cell repairs the cut: NHEJ joins the ends and often knocks the gene out with a frameshift, while HDR copies a repair template and can correct a faulty base. A third tab covers uses and ethics: the 2023 sickle-cell therapy, edited crops, research models, somatic versus germline editing and the 2018 edited babies.
Lesson: Gene editing with CRISPR-Cas9: guide RNA, PAM, double-strand cut, NHEJ and HDR repair, knockouts, applications and ethics
What it shows
CRISPR-Cas9 lets scientists cut DNA at one chosen place. A guide RNA carries a sequence that pairs with the target DNA, and Cas9 cuts both strands only where the target sits next to a short sequence called the PAM. The cell then repairs the cut. Joining the ends directly (NHEJ) often adds or loses a few bases and switches the gene off; copying a supplied template (HDR) can put in a correction. This model uses made-up DNA drawn as coloured blocks, a 10-base guide instead of about 20, and illustrative cutting and repair rates.
How to use
On 1. Find and cut, choose the Guide RNA in Cas9 and press Run to watch Cas9 check each PAM site; tap a site for its close-up. Test in 100 cells records the cuts in gene X and gene Y. On 2. Repair, choose the Gene in the cells, tick Add a repair template if you like, then press Run for one cell or Repair 100 cells. On 3. Uses and ethics, choose Cells edited and an Example.
Parameters you can change
- View 1. Find and cut, 2. Repair, 3. Uses and ethics
- Guide RNA in Cas9 Guide A, Guide B, Guide C, Guide D
- Gene in the cells Working gene, Faulty gene (one base changed)
- Add a repair template
- Cells edited Body cells (somatic), Embryo (germline)
- Example Sickle-cell therapy (2023), Edited crops, Research models, Edited babies (2018)
Questions to explore
- Guide B pairs perfectly with part of gene X, yet Cas9 never cuts there. What is missing next to that stretch?
- Why does losing one base at the cut usually switch the gene off, while losing three bases often does not?
- Why is an edit made in an embryo passed to future generations, but an edit made in blood stem cells is not?
