I might have misunderstood the way CRISPR-Cas9 experiment works, but what I understood is that, alongside other things, a gRNA is used to "guide" the Cas9-protein into:

• Cut at the right position
• Make the cell build a new DNA sequence at the position

I found a lot of examples of tools, such as CRISPRSeek, that are used to select gRNAs that will correctly guide the Cas-9 protein in accordance with the purpose of the experiment.

Now what I don't really understand is where does the gRNA comes from, and what are the possible composition of gRNAs?

For an experiment, it is apparently bought to some companies. According to this article:

sgRNA can be synthetically generated or made in vitro or in vivo from a DNA template.

So is it possible to synthetize any gRNA (any chain of ATCG basis)? This sounds somewhat "magic". Wikipedia article mentions mitochondries, are they te "pool" where to get gRNAs?

In a CRISPR-Cas9 experiment, the protein cuts the site matching the cRNA part of the gRNA. My question is: How many cuts are possible if multiples sites matching the cRNA are found in the cell?

Especially, considering DNA is made of multiple chromosomes, if more than one chromosome have a site matching the cRNA, will they all be cut? Does it depend of the quantity of Cas9 protein brought in during the experiment (meaning is some Cas9 protein "consumpted" at each cut)?

I might have misunderstood the way CRISPR-Cas9 experiment works, but what I understood is that, alongside other things, a gRNA is used to "guide" the Cas9-protein into:

• Cut at the right position
• Make the cell build a new DNA sequence at the position

I found a lot of examples of tools, such as CRISPRSeek, that are used to select gRNAs that will correctly guide the Cas-9 protein in accordance with the purpose of the experiment.

Now what I don't really understand is where does the gRNA comes from?

For an experiment, it is apparently bought to some companies. But how does they get it? My hypothesis:

• Is it synthetized ? If yes, how?
• Is it "taken" from organisms (wikipedia about gRNA mentions mitochondries), and if yes how?

I might have misunderstood the way CRISPR-Cas9 experiment works, but what I understood is that, alongside other things, a gRNA is used to "guide" the Cas9-protein into:

• Cut at the right position
• Make the cell build a new DNA sequence at the position

I found a lot of examples of tools, such as CRISPRSeek, that are used to select gRNAs that will correctly guide the Cas-9 protein in accordance with the purpose of the experiment.

Now what I don't really understand is where does the gRNA comes from, and what are the possible composition of gRNAs?

For an experiment, it is apparently bought to some companies. According to this article:

sgRNA can be synthetically generated or made in vitro or in vivo from a DNA template.

So is it possible to synthetize any gRNA (any chain of ATCG basis)? This sounds somewhat "magic". Wikipedia article mentions mitochondries, are they te "pool" where to get gRNAs?