In the "The Origin of Species," Darwin explained his theories on genetics based on what he saw. He focused on traits expressed by animals. This would eventually lead to more focused genetics studies.
Gregor Mendel, also known as the Father of Genetics, studies and experiments on peas. He comes up with the terms "recessive" and "dominant." He also believes there to be "invisible" things that determine traits.
Friedrich named DNA "nuclein" while studying leukocytes.
Phoebus Levene discovers deoxyribose sugar in the nucleotides. Then he discovers that nucleotides make up DNA.
William takes the first X-RAY diffraction pictures of DNA.
Oswald Avery first isolated DNA as that which makes up genes and chromosomes. He also found that DNA was the one involved in the transformation of bacteria and not proteins. Two other people helped in his work, Colin MacLeod and Maclyn McCarty.