In this paper Mendelian genetics is reinterpreted in terms of mathematics. The gene in many living things ‐‐ but in by no means all of them ‐‐ is here viewed as an ordered pair of elements (called alleles), and each offspring as an element of a Cartesian product. The paper illustrates how this view provides a means of presenting both instances of classical Mendelian inheritance and also special cases of inheritance.