The major, basic models of genetic theories are for the first time reconstructed in a precise and perspicuous way. The book aims at foundational clarification. It shows how the different branches of genetics are systematically related, how they differ from each other, and how they can be compared with each other. The models may serve as a basis for top-down computer implementations and for teaching genetic theory. They will be of value in genetics, biology, medicine, and the philosophy of science, but also in ethical discussions.