It doesn't— The mutant gene is still there, it's just not being expressed. It doesn't change what I am, just how I look.

[ Although, it does change who he is a little bit, doesn't it? After all, look what the serum does to Charles...

He can't help but notice the growing flames on the candles, eyes narrowing nervously. ]

Let me guess. You're doing this? Your mutation's, what, fire related?