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P.A. Levene
During the 1920s, Levene determined the basic structure of the nucleotides that compose DNA and RNA- the two nucleic acids found in living cells. In DNA there is deoxyribose, a phosphate, and either adenine, guanine, cytosine, or thymine. In RNA there is ribose, a phosphate, and either adenine, guanine, cytosine, or uracil. -
Frederick Griffith
Frederick discovered that one strain of the bacteria that causes pneumonia could be transformed into the second form. Griffith performed experiments on mice and different strains of bacteria. He ultimately concluded that the genetic material must be something other than protein. -
Oswald Avery
Oswald helped to identify the molecule that transformed the one strain into the second in Frederick Griffith's experiments, through isolating macromolecules and exposing them to the strains. Avery figured out that when the second strain of bacteria's cells were killed, DNA was released. Since the first strain had some DNA in their cells, this changed them into the second strain. -
Erwin Chargaff
Erwin Chargaff, using data from Levene's studies, analyzed the amount of adenine, guanine, thymine, and cytosine in the DNA of different species. He found that the amount of guanine almost equals the amount of cytosine, and the amount of adenine nearly equals the amount of thymine (aka Chargaff's rule). -
Rosalind Franklin
Franklin took the famous Photo 51 that shows the characteristics of helix structure. This was used in Watson and Crick's research. She also worked extensively with X-ray diffraction- a technique that involved aiming X rays at the DNA molecule specifically.. -
Linus Pauling
Pauling published papers on his findings of the structure of proteins. He studied polypeptide bonds and the helical structure of proteins. Although he didn't work out the correct DNA structure, he was still very important to the ultimate discovery of it. -
Hershey and Chase
Hershey and Chase provided definitive evidence that DNA is the transforming factor in Griffith and Avery's experiments. Their experiments involved bacteriophage made of DNA and protein. You must remember that viruses have to inject their genetic material into a living cell to reproduce. Through radioactive labeling, they traced the DNA and protein throughout their experiment to determine that DNA, not protein, was the genetic material that is passed on. -
James Watson and Francis Crick and Maurice Wilkins
These men built a double helix model of DNA and suggested the method of semiconservatice replication. They supported each others' theories of the structure for DNA and methods of replication until they were ready to present it.
