You can do a lot with chromosomes, but the question is how it is communicated to the player in an understandable way,
especially if a player can only see the stats of a monster and not it's individual chromosomes.
I'd keep it simple and add one (small) negative stat and one (bigger) positive stat to each chromosome.
Small side-effect will be that incest will give a chance of getting the same chromosome double, and giving a monster double the penalty,
which can be quite the disadvantage and actually is why incest is bad irl.
(it can also be advantageous as the positive stat also goes double, so you get specialized monsters)