All of the pathways are together for anatomy block (anatomy, histology, and embryology), and lectures are mandatory for everyone during that time. Attending LDP lectures as an ISP student really isn't all that helpful. In fact, they'll usually confuse you more than anything else, as the LDP people tend to get a lot more extra "fluff" in their lectures that you won't have to cover in your modules. Also, while you can switch to LDP at any time, you might not be able to switch back to ISP ever again. Once you leave a pathway, you lose your spot, and ISP usually has a waiting list for people to switch into it.
As for genetics, you'll be fine with just the module. I had never taken it before (or any upper level biology or biochemistry courses for that matter), and I managed to get an A. It's taught by Dr. Bradbury, so the module is very well put together, although very dense. Just hope that you get more than five days next year--they did it the week of our white coat ceremony this year, so we had literally five days to learn like fourteen chapters... I would say biochemistry and physiology are the worst ISP modules of core. Can't say much for systems yet, since we've only really had MSK.