A common polymorphism in the alpha-actinin-3 (ACTN3) gene results in the lack of ACTN3 protein expression in fast twitch muscle fibers in ~16% of the human population (1). This genetic change has been linked with muscle performance in humans (2) but does not cause any known muscle disease (1). We have developed a series of laboratory modules that provide an authentic classroom research experience and which address the connection between science and society by examining the implications of ACTN3 genetic testing to improve sports training and performance. This article accompanies the lesson "The ACTN3 Polymorphism: Applications in Genetics and Physiology Teaching Laboratories," and summarizes background information that an instructor would need to implement the project in class.