Biologic: Gene circuits and feedback in an introductory physics sequence for biology and premedical students

Abstract

We describe an educational module on feedback and gene circuits that constitute the final topic in a new year-long introductory physics sequence aimed at biology and premedical students at Yale University. The overall goals of this sequence are threefold. First to demonstrate the application of physics and mathematics in the life sciences. Second to introduce biological science majors to mathematical and physical tools, principles, and experiences. Third to seed an enduring appreciation of quantitative approaches in biology and medicine. Here, we present a module on feedback and gene circuits that focuses on a genetic toggle switch and a repressilator. The genetic toggle switch consists of two genes, each of whose protein products represses the other's expression, while the repressilator consists of three genes, each of whose protein products represses the next gene's expression. Analytic, numerical, and electronic treatments of the genetic toggle switch show bistability. A similar treatment of the repressilator reveals sustained oscillations.