Probably a waste of time. Unless you're really interested in it and you truly have a passion for it, I'd say to avoid double majoring. A basic BS in Biology should be more than enough for any job you'd get as a "Genetics" major. Same vice versa, especially if you plan to just apply to medical school in the end. It's assumed you understand the principles deep enough, especially since any project/work you get involved with will require a more refined and narrow focus anyways.
If you really want to double major pick something more distant from bio, you'll at least have the advantage (slight, if any at all) of coming off as having someone with slightly more dimensions. Your GPA will also be kept from being slaughtered as is traditional of STEM curriculum at many schools.