Thanks for that analogy sweballp, It helped me make sense of it all, I was over simplifying the genetics and assuming the spinner only had spider and pinstripe genes (only one bag of marbles, containing spider and pinstripe), but the way i understand it now is that the spider and pinstripe genes are at different loci, (in different bags), and something is inherited from each loci (or bag of marbles). This made a lot of sense to me.