Gregor Mendel discovered the basic principles of heredity after breeding pea plants for 8 years
Theodor Boveri and Walter Sutton Developed the chromosome theory of inheritance.
Thomas Hunt Morgan discovered the white eye mutation while breeding fruit flies.
Frans Janssen observed chiasmata before the first division of meiosis.
Barbara McClintock discovered transposition.
James Watson and Francis Crick discovered the double helix structure of the DNA molecule.