Hi Renjith,

CRISPR-Cas9 is a complex formed by a little RNA sequence that will target one selected region/gene on the DNA, and enzymes that will cut the the DNA at the targeted sequence that will be repaired (depends on the protocol, you can delete some sequence or add some sequence). whatever, it will change the target and its impact on the cell regulation. On the other hand, there are some side effects since the RNA sequence is too small to ensure specific targeting (about 20 bases), that's why you often hear off-targets. other parts of the genome could/will be touched.

fred

Hi,

I'll try using simpler terms than Frederic. In case you didn't know, bacteria can also be infected by "viruses" (a more appropriate term would be "phages"). These phages insert their genetic material inside the bacterial cell and it is generally integrated in the bacterial chromosome. I won't bother you with the details of a phage infection but the important thing to know is: bacteria developped a defense system against them. A protein complex (CRISPR-Cas) has this role of localizing a specific DNA target (for example a sequence in the phage DNA) and cut it. Several researchers had the idea of using this as a genetic editing tool. If you can "tell" the CRISPR what to target, therefore you can edit pretty much anything. Of course, once the DNA is cut, another machinery will help repair it... but the cool thing is you can "give" any DNA template for the repair, so that the "cut" will actually be a "cut and replace". Here you go, hope that helped!

Romain

Hi there

CRISPR is a primitive immune system developed by bacteria to defend themselves against viruses. The idea is simple: when infected by viruses, bacteria are able to integrate portions of the genome of the viruses within their own genomes. In the case of a recurent infection of the same virus, the inserted portions of virus genomes will be transcribed to produce a RNA molecule, that will be used by the bacteria to target and degrade the infecting genome. The responsible for the degradation of the viral genome is a protein called Cas, which will recognize the virus DNA together with the generated RNA, which will bind to the virus genome by Watson-Crick complementarity.

The funny thing about this system is that if you are able to design a RNA complementary to a given DNA, Cas protein will cleave the target DNA. For this reason it is used in "genome editing" protocols. It works wonderful in any kind of cell, human, plants, etc. Cleaving a genomic DNA in a specific region could facilitate deletions or homologous recombinations with a high efficiency. So, you can virtually "copy and paste" anything in whatever location of a specific genome.

Hope it helps. Best