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Miescher
While Miescher was researching white blood cells, he collected bandages with pus on them to examine a new molecule called nuclein. He was able to figure out what nuclein was made of and how the ratio is different each time. He realized that proteins were the molecules of heredity. Before scientist didn't know where DNA came from but Miescher's research proved DNA came from the nuclein which is inside the nucleus. -
Chargaff
Chargaff was convinced to study DNA from Avery's theory that the heredity code that our parents pass onto their offspring is made of DNA. He discovered the Chargaff Rule which states, the amount of purine is equal to the amount of pyrimidine in DNA. He made this discovery by using partition chromatography to separate it into its components for analysis by ultraviolet spectrophotometry. -
Chargaff continued
Chargaff pictured the DNA as a Moebius strip which splits on the center line with two separate halves of the parent strip. -
Franklin
It turns out Franklin was the one who gathered the data that proved that the shape of DNA can be described as a double helix. Franklin and her partner, Gosling found two different forms of DNA in the X-ray. Sample "A" was the dyer form which seemed to show more detail. Sample "B" was the wetter form which she set aside to study later. Sample "B" showed images of a definite helical structure that had two clear strands visible, she labeled this sample "Photo 51." -
Franklin continued
Watson and Crick held a conference about the structure of DNA. Franklin attended and thought their theory had no evidence unlike her theory. Later Franklin moved and lost track of "Photo 51" and it ended up in Watson and Crick's hands. They used "Photo 51" in their book "The Double Helix" to prove the structure of DNA. Even though Franklin should get credited with the discovery of DNA structure, Watson and Crick won the Nobel Prize. -
Hershey & Chase
Hershey and Chase discovered that DNA is genetic material. Before the many experiments they conducted, scientist thought DNA was carried in proteins. In their experiment they used a virus called phage to prove that DNA had to be genetic material rather than proteins. -
Watson and Crick
These two men worked together to discover the double helix in DNA. This explains how DNA replicates itself and how hereditary information is coded on the DNA. In order to study DNA they used a X-ray diffraction. Later it was proven that they took Franklin's evidence, "Photo 51" and published it in their book. -
Meselson & Stahl
Michelson and Stahl made an experiment known as "The Most Beautiful Experiment in Biology" which proved how DNA replicates. Before this experiment there were three theories that scientist argued over which one was correct; they were called conservative, dispersive, and semi- conservative. They proved that DNA replicates through the semi conservative theory which is where a DNA strand separates to act as a template to copy and serve as a new strand.
