I need some help on what exactly is happening here at the cellular level. I understand that incomplete dominance is a blending, for example caused by a functional enzyme producing pigments and a non-functioning enzyme. The result would be less pigments, therefore an apparent mixing. But what is happening with co-dominance? You have checkered chickens and roan cows. How exactly is this caused at a cellular level? If both phenotypes are active simultaneously, shouldn't there be a uniform blending instead of having patches of colour or similar phenomena?