but my next pick would be homosexual - that's just the vibe I get from him though :) I could be wrong.

*Takes question in literal, scientific terms.*

Sheldon uses his own DNA to produce other Sheldons. When that happens, he will invade the planet, reproducing at an exponential rate no sexual reproduction could achieve. Asexual reproduction is clearly the the best choice, especially when you have a genetically perfect specimen like Sheldon. You don't want to corrupt that DNA with any other inferior being's.

;o) ;o)

Either that or he's straight and just doesn't care. I mean, he wouldn't understand homosexuality because we saw in The Maternal Capacitance that doing it soley for reproductive purposes was "a fairly efficient arrangement." He would see no point in others doing it (and I say others because he doesn't give a darn) unless they were trying to procreate.

I don't think there's a current term to describe Sheldon, but this would be the closest.

Either this or heterosexual.