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Miescher
-He was the first to identify DNA as a distinct molecule
-Miescher collected bandages from a nearby clinic and washed off the pus. He experimented and isolated a new molecule (nuclein) from the cell nucleus. He determined that nuclein was made up of hydrogen, oxygen, nitrogen and phosphorus> nucleic acids -
Chargaff
-analyzed the base compositions of DNA in cells and discovered that the amounts of adenine and thymine are almost always equal as are to guanine and cytosine
-his discovery was that it helped Watson and Crick in their determination of the structure of DNA. They reasoned that because adenine and thymine always exist in the same proportion, they must always bond together, and similarly for cytosine and guanine. This conclusion led them to propose a double helix structure for DNA -
Franklin
-Recorded a critical X-ray diffraction pattern and demonstrating that DNA is in the form of a helix
-Franklin analyzed two sets of photos of crystallized DNA fibers. She used two different fibers of DNA, one more highly hydrated than the other. From this she came to the conclusion of the basic dimensions of DNA strands, and that the phosphates were on the outside of what was probably a helical structure. -
Hershey & Chase
- Confirmed that the genetic material of viruses is DNA not protein -Hershey and Chase able to prove that the DNA from the phage is inserted into the bacteria shortly after the virus attaches to its host. Using a high speed blender they were able to force the bacteriophages from the bacterial cells after adsorption. -concluded that DNA, not protein, was the genetic material. They determined that a protective protein coat was formed around the bacteriophage
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Watson & Crick
-Published their model of the DNA double helix...the model was made possible by Franklin's work.
-by trying to disprove the DNA model presented by chemist Linus Pauling, they determined that the structure of DNA was a double-helix polymer, or a spiral of two DNA strands, each containing a long chain of monomer nucleotides, wound around each other -
Meselson & Stahl
-They were especially interested in trying to devise a way to prove or disprove Watson and Crick's model of semi-conservative replication and so invented the technique of density gradient centrifugation (which uses centrifugal force to separate molecules based on their densities) and used this to prove that DNA is replicated semi-conservatively
