How to compare multiple groups with count data?

Question

[Camilo Andres]

Hi! So sorry if this question doesn't completely fit the "bioinformatics" topic, but I didn't know where else to post it. I'm trying to compare the mutation frequency of a set of genes for three different cohorts (one of them being a very small one), which one is the more appropriate method to do it? should I perform a one to one Fisher's test for every gene?

Thanks in advance