I'm going to assume you have read this... http://ball-pythons.net/forums/showt...Basic-Genetics
well what happens with genes such as lesser/butter, mojave, russo, ect is they all sit on the same locus. When you breed a butter/mojave to a normal, the butter/mojave gives one allele or the other, can't give both, can't give none. It's like when you have a super butter, it gives 1 butter allele or the other butter allele, not both, not none.