Dahyun week10
How CRISPR lets you edit DNA
CRISPR functions as a bacterial immune system. CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats, which is essentially a collection of DNA sequences from viruses that have invaded the bacterium in the past.
The bacterial immune mechanism works as follows:
- Cas proteins, related to CRISPR, cut the DNA of the virus.
- The cut DNA is then added to the bacterium's CRISPR section.
- This DNA is copied into short RNA segments.
- The RNA binds to the Cas9 protein.
- If the same virus invades again, Cas9 compares it to its bound RNA and destroys it if they match.
For RNA viruses, reverse transcription is used to convert RNA into DNA, which is then added to the CRISPR sequence.
To use CRISPR for cutting a target site, guide RNA is created and attached to Cas9. This allows Cas9 to locate and cut the target. However, the process of joining the cut ends can lead to errors, such as the addition or deletion of bases. To prevent this, a sample DNA sequence can be added to the CRISPR mixture. This allows for repair based on the sample through homology-directed repair.
