basics of triploid reproduction:

First off: three sexes; male, female, and unix. The male and unix mate with the female through different orifices and ways. The female can mate with both at once or seperately, having the ability to store the sperm and its unix equivalent until carrying a complete set, and then self-inseminating. The female would first inseminate with one sex's haploids (which had one way of getting into the egg), and then the other sex's (which has another way of getting in). All three combine in egg to create a complete triploid organism.

Dominance of a trait is determined through normal means. In order to account for duplicates, one is methylized by a special checking RNA.

NOTE: this was posted here to clarify (take it off of) an IRC argument