Discoveries

Esther was the sole author of a 1952 paper reporting experiments with lactose metabolism genes (Ferrell 2018). She analyzed Lac+ recombinants from Lac− x Lac− crosses for stability of the Lac+ trait. She examined over 31,000 recombinants and found only one exception, which led her to conclude that Lac+ reverse mutants are usually stable. However, she also identified another genetic category: an unstable suppressor mutant that is able to “mimic wild type by suppressing the effect of Lac1− mutation.” 

The Lederberg lab discovered generalized transduction in Salmonella in 1952, and it was published by Joshua and Norton Zinder. Some genetics textbooks have mentioned that Esther participated in this discovery, however she was not included as an author of the article (Ferrell 2018). Please see Academic Career for more information.

Thanks to their replica plating technique, Esther and Joshua found strong evidence for “the participation of spontaneous mutation and populational selection in the heritable adaptation of bacteria to new environments,” finding that mutant strains resistant to bacteriophage T-1 and the antibiotic streptomycin were part of normal variation in the E. coli population, even without selection for their traits (Ferrell 2018). This experiment refuted Lamarck’s idea that genetic traits change in response to the environment, and thus, it was important in modern genetics’ understanding of mutation as a random process rather than occurring due to need. Learn more about the technique here: Replica Plating