It is probably not a single gene.
But the amount of mutations / off average development has a higher
probability for men, as the genepool is not as static (just one X cromosome)
This also yields a higher probability to have a genetic combination that
creates a genious.

This probably also has an evolutional reasoning.
Men have the higher probability to bear genetic mutations.
So men with a "good" new combination have more offspring in
the competition for sex.
Females are likely to have the same number of offprings as other females.

So the female genepool is better off to have a smaller probability for mutations
than the male genes.