Question: how did you make a mutant zebrafish?

Elliot Jokl answered on 16 Jun 2016:

Thanks for the question!

The way we make mutations in general is using a technology called CRISPR/Cas9 genome editing. The way this works is that you design a molecule that will stick to the fish’s DNA in a specific place, where you want to mutate the gene. This molecule brings in an enzyme that cuts the DNA. When the fish cells try to put the DNA back together, they make mistakes, and these are the mutations.

How we get this to work in fish is to inject these molecules and the enzyme directly into a zebrafish embryo. We have to use a really thin glass needle and a special microinjection machine to inject a tiny amount into the embryo when it is only a small number of cells. I usually inject a couple of nanolitres into each embryo. So you would need 500,000,000 of these tiny little injections to fill a liter bottle! Which is my way of saying it is very fiddly work and it took me a long time to get the hang of it.

When the fish has grown up, you can take a little bit of its tail fin (this doesn’t hurt the fish, and it actually grows back!) and test the DNA to see if the experiment has worked and you have mutations.