Calvin Bridges? Experiments on Nondisjunction as Evidence for the Chromosome Theory of Heredity (1913-1916)

From 1913 to 1916, Calvin Bridges performed experiments that indicated genes [5] are found on chromosomes. His experiments were a part of his doctoral thesis advised by Thomas Hunt Morgan [6] in New York, New York. In his experiments, Bridges studied Drosophila [7], the common fruit fly, and by doing so showed that a process called nondisjunction caused chromosomes, under some circumstances, to fail to separate when forming sperm [8] and egg [9] cells. Nondisjunction, as described by Bridges, caused sperm [8] or egg [9] cells to contain abnormal amounts of chromosomes. In some cases, that caused the offspring produced by the sperm [8] or eggs to display traits that they would typically not have. His research on nondisjunction provided evidence that chromosomes carry genetic traits, including those that determine the sex of an organism.