Quote Originally Posted by Freakie_frog View Post
Correct but its not dominate in the fact that it still produces the wild type offspring so in a since its not. A true Dominate gene would have no super and not produce any normal offspring.
Ed, that's not correct. Spider is a dominant gene. It truly is, however most spiders are hets, and they do not pass all spiders because of the way genes are inherited.

If each animal receives one copy of a gene from the parents, using the heterozygous spider as an example, what guarantees that this "dominant" gene is the one that gets passed along to the offspring and not the normal gene?

A gene can be dominant, but that in no way means that there will be no normal offspring unless the animal is homozygous for that gene.