During the first decade of the twentieth century, Lucien Cuénot's ingenious crossbreeding experiments on mice provided proof that Mendel's newly rediscovered laws applied to animals as well as to plants. His research on the crossbreeding of yellow mice provided the first example of the existence of lethal genes.

Cuénot studied at the Collège Chaptal where he earned his bachelor's degree in science, before enrolling at the Faculty of Sciences of the Sorbonne in 1883. Regarded as a brilliant student by his professors, Cuénot placed first in his examinations and earned his doctoral degree in the natural sciences in 1887. In 1888, he was appointed assistant in comparative anatomy and physiology at the Faculty of Sciences in Paris. Although he intended to study medicine, Cuénot changed his plans when he was offered a position as lecturer in zoology in Lyons. Two years...