This discussion document defines the gametic entropy of a population. It is a precise interpretation of a phenomenon occurring at the intersection of population genetics and information theory. This interpretation challenges minor statements in two journal articles. Gametic entropy is the application of Shannon entropy to the genetic information carried by gametes in the propagation of a population. This document serves as a reference to facilitate discussion. The practical utility of gametic entropy is not covered in this document. Understanding of Shannon entropy and genetics is required to understand the entire document.