Storm wasn't a goddess. She was a human mutant with the ability to manipulate and duplicate various weather patterns via telekinetic manipulation of air flows, particularly those involved in electrical storms. An African tribe mistook her for their rain goddess as a child and she grew up, understandably, with something of a god complex.

(Unless that got retconned, I guess.)

That's the comic Storm, incidentally; I never got around to watching the films.

However, in the comics, so-called "mutant" abilities are genetic "mutations" somehow hidden in human "junk DNA", placed there by prehistoric aliens (for some reason.) These "mutations" (probably in-universe slang BTW) are often only minor alterations to the affected individual's biology, since the MU has a lot of strange physics, like psychic powers , alternate worlds, functional magic etc. that make them easier. These powers are usually "latent" and inactive, only manifesting when "triggered" by radiation, electrical shocks, physical injuries or whatever, and this is often mistaken for said "trigger" actually mutating them into super-humans. Whether this is possible or not is debatable, but it always irritates me when people go "those idiots at Marvel think radiation will mutate you into Superman! Ha ha, how superior we are." and such. (Not saying that was your intention.)

Again, this applies to the comic continuity, and I know nothing whatsoever about the films. But you have to admit "The genetic code ... for mutation" makes much more sense if they were aiming to reference this.

(sorry for replying to a 2007 comment, but I hate to think you'd go off thinking this was an example of the uneducated masses thinking evolution consists of animals somehow mutating fully functional organs etc. not present in the parents.)