Punnett squares and hybrid crosses: how Mendelians learned their trade by the book

Abstract

AbstractThe rapid reception of Gregor Mendel's paper ‘Experiments on plant hybrids’ (1866) in the early decades of the twentieth century remains poorly understood. We will suggest that this reception should not exclusively be investigated as the spread of a theory, but also as the spread of an experimental and computational protocol. Early geneticists used Mendel's paper, as well as reviews of Mendelian experiments in a variety of other publications, to acquire a unique combination of experimental and mathematical skills. We will analyse annotations in copies of Mendel's paper itself, in early editions and translations of this paper, and in early textbooks, such as Reginald Punnett'sMendelism(1905) or Wilhelm Johannsen'sElemente der exakten Erblichkeitslehre(1909). We will examine how readers used copies of such works to reproduce the logic behind Mendelian experiments, either by recalculating results, or by retracing the underlying combinatorial reasoning. We will place particular emphasis on the emergent role of diagrams in teaching and learning the practice of Mendelian genetics.