[Well, she doesn't get what he meant by accident. He should probably explain it better.]

Yeah, like I said. It's an accident. When a person is first conceived, everything about how they will grow is in their genetic code. Whether you would have brown hair, blue eyes, dark skin, or even be a girl, right? That's how it's supposed to be. But for mutants... when all that happens, something else happens. So we end up... different. But it only happens to very, very few people.