When the German chemist Emil Fischer presented his lock-and-key hypothesis in 1899, his analogy to describe the molecular relationship between enzymes and substrates quickly gained vast influence and provided future generations of scientists with a tool to investigate the relation between chemical structure and biological specificity. Rebecca Mertens explains the appeal of the lock-and-key analogy by its role in model building and in the construction of long-term, cross-generational research programs. She argues that a crucial feature of these research programs, namely ascertaining the continuity of core ideas and concepts, is provided by a certain way of analogy-based modelling.

Rebecca Mertens (PhD), born in 1984, is a postdoctoral researcher in the history and philosophy of science at Bielefeld University. She works on the role of analogies, models and forms of comparison in the history of molecular genetics and is a member of the collaborative research program 'Practices of Comparison: Ordering and Changing the World'.