Experimenting with common garden peas, Austrian monk Gregor Mendel shows how traits like color and height are passed from one generation to the next.

Swiss scientist Fredrich Miescher discovers DNA — what he calls "nuclein" — in human pus from hospital bandages.

The term genetics is first used in a letter written by biologist William Bateson, an early proponent of Mendel's ideas.

Danish botanist Wilhelm Johannsen coins the word gene to describe the Mendelian units of heredity. The word derives from the Greek genos, meaning "birth".

Studying genetic mutations in fruit flies, embryologist Thomas Hunt Morgan shows that genes are carried on chromosomes, a finding that earns him a Nobel Prize.

Oswald Avery, Colin MacLeod and Maclyn McCarty show that DNA — not protein, as many scientist thought — carries hereditary information.

On Feb. 28, American biologist James Watson and British physicist Francis Crick deduce that the three-dimensional structure of DNA is a pair of intertwined spirals — a "double helix.''

Crick and other scientists begin to map how DNA's sequence dictates the creation of certain proteins.

Hamilton O. Smith and others lay the foundation for modern genetic engineering by discovering that "restriction enzymes" can slice DNA into snippets.