IMM340/350 are definitely memorization.

IMM340 was memorization for the most part. This course was mostly like the steps in a particular processes (forming antibodies, how receptors are made, etc.). There is one section of IMM340 at the end that makes up half of the exam that's not memorization. It's like applying all of the experiments and results this one professor has taught you to see the outcome of your own kind of experiment. Most people struggle with this the most, but once you've got it, studying for the exam takes like 1-2 days max.

The first part of IMM350 is a lot of nit-picky details (which transcription factors trigger which T-cell differentiation). The second part, however, is more like applications of IMM in real life (transplants, allergies, autoimmune diseases, cancer), and these profs made their exam questions more general and bigger picture. With that said, they had a lot of slides lmao, many not tested lol.

Overall, I didn't find these courses to be difficult, but you do have to memorize. All multiple choice though, so the answer's there! I'm not too sure about the fourth year courses, but I believe those tend to be more application based.

I'm in MGY too, but more of the microbiology than the genetics part. But I don't find either majors to be hard; I think the reputation for their difficulties come from the fact that the specialist programs are more intense. Also, probably because IMM250 is not representative of 340/350. Most people think those courses will be just as easy as 250 to finish the minor, but are (regretfully) mistaken. You just kinda have to know what you're getting yourself into! Helps if you're interested in the material too.