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Discovery of Nucleic acids
Friederich Miescher, a swiss phisician and biologist, first isolated the genetic material from white blood cell nuclei, he denominated it as "nuclein" because of its acidic nature. -
Discovery of the DNA's components
Shortly after, Phoebus Levene, a biochemist, discovered and determined all the components of DNA, and then defined the nucleotides, phosphate-sugar-base units.
However, his idea of the structure wasn't right, since both his takes were incorrect. -
Friederick Griffith Transformation Experiment
Friederick Griffith, former bacteriologist, performed an experiment by using two strains of Streptococcus. However, his first question was not answered by the experiment, hence it was later proven by Oswald Avery, Colin MacLeod and Maclyn McCartly. (1944)
Together, they determined what was the transformation by mixing one of two enzymes. This experiment showed how DNA was the responsible for the transformation. -
Photography 51
Rosalid Franklin took a lot of great photographs of the B form of DNA. This was the most famous image that she got, which was called “Photo 51”, which shows really clearly the x of the double helix from the top.
She was unsure to present this piece of information, however, Maurice Wilkins stole the Photo 51 from her desk, and got it for Watson and Crick, who by seeing the picture knew why their model was previously wrong. -
Double helix? Triple Helix?
In 1951, Watson and Crick wrote a paper describing DNA as a double helix with sugars and phosphates at the center, and the nucleobases facing the outside, however, it was proven to be incorrect.
Linus Pauling came up with a triple helix model, but he was incorrect as well. -
Hershey-Chase Experiments
Martha Chase and Alfred Hershey started experimenting with phages, viruses that infect bacteria.
By using a bacteria cell, they allowed the phages to infest them, by then separating what was in the bacteria from what wasn't in it by centrifugation. Thanks to the experiment, they concluded that it was not the protein that was the genetic material, but DNA. -
Counting Nucleobases
Edwin Chargaff started counting nucleobases, and started to notice that something was off. By making percentages of the Thymine, Adenine… he discovered a pattern in every subject he tested.
Chargaff's rule, or what they called it, showed that Adenine and Thymine were always in balance, and Cytosine and Guanine were always balanced as well with each other. Edwin then shared his discovery with Watson and Crick, who left Chargaff out of all recognition of the discovery of DNA. -
Lies, Thieves, and DNA
Watson and Crick later on finally built the model based on Rosalid's image. Three different articles were then published, which lead the whole group to be awarded a Nobel Prize. However, Rosalid never got to receive the award, hence to her passing. Neither of the three acknowledged her work in their discovery.