Born in 1939, Dennis trained as a biochemist at MIT (PhD 1967) and as a neurobiologist at Harvard Medical School with Steven Kuffler. He worked under Francis Crick and Sydney Brenner at the MRC LMB in Cambridge in 1969 before moving to the MRC Biophysics Unit in 1972. Here he studied the neural outgrowth and cytoskeletal transport and discovered actin, myosin and the role of mechanical tension in neurons.

In 1991, following a sabbatical visit to Caltech, he made a paradigmatic change to computational biology. He became interested in mathematical modelling of bacterial chemotaxis, thus pioneering systems biology, and moved to University of Cambridge where he remains an Emeritus Professor. In 2006, he received the Microsoft European Science Award for his work on chemotaxis in E. coli.

He is a founding co-author of the seminal textbook Molecular Biology of the Cell, author of Cell Movements, and a writer of the thoughtful popular book Wetware: a Computer in Every Living Cell (2009). In 2022, one US website named him the ‘6th most influential scientist on the planet’, a proposition he disputes.