Werewolves are the vassals of Hircine,the Daedric Prince of the Hunt,are they not? So it stands to reason that Hircine,being a godlike being,can kick pesky things like genetics,so long as it falls within their sphere of influence.
Meh. I didn;t really like being a lycan in Bloodmoon,and I HATED being a vampire in Morrowind and Oblivion (Never figured out how to join a vampire clan in Morrowind). So,I tend to avoid lycanism and vampirism like the plague in TES.