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Miescher
Date of Discovery: 1869
Contribution: Miescher isolated a new molecule, "nuclein" which is DNA with associated proteins, from a cell nuclei. He determined that nuclein was made up of hydrogen, oxygen, nitrogen, and phosphorus.
How Discovery Was Made: He researched the composition of lymphoid cells-white blood cells-, which are found in great numbers in pus. He used pus off bandages to research.
This discovery added to our understanding of DNA because it was the first discovery of DNA. -
Chargaff
Contribution: Came up with two rules:
1.In natural DNA the number of G units equals the number of C and A numbers equal T numbers.
2.The composition of DNA varies from one species to another, in particular in relative amounts of A,G,T,and C.
How Discovery was made: Looked at the composition of DNA from many organisms and realized that in all species, A was equal to T and G was equal to C, roughly.
This discovery added that DNA has base pairs and that one strand fits with the other strand. -
Franklin
Date of Discovery: 1951
Contributions: Franklin worked on figuring out the composition of a DNA model and came up with an x-ray photo of a DNA molecule that was a double helix. She discovered the phosphate units were located in the external part of the molecule.
How Discovery was made: She used small models and used x-ray diffraction data to make her discoveries.
This showed us how the DNA is structured so we may be able to learn more about the DNA and maybe why it does what it does and other. -
Hershey and Chase
Contribution: They confirmed that DNA is genetic material. At the time, people thought that proteins were genetic material because DNA seemed simpler than proteins.
How Discovery was made: They conducted experiments that showed the when bacteriophages, which are made of DNA and proteins, infect bacteria, their DNA enters the host bacteria, but most of their protein does not.
This added to our knowledge because we now knew that we get our DNA from our parents, but we didn't know exactly how. -
Watson and Crick
Contributions: With the help of Franklin (they used her work) Watson and Crick reached the conclusion that DNA molecules exist in a 3D double helix model.
How Discovery was made: They used cardboard cutouts representing individual chemical components of the 4 bases. They shifted molecules on their desktop like a puzzle.
This discovery added to the knowledge of DNA because we now got a more detailed description of the model so we can understand how we get our genetic information from our parents. -
Meselson and Stahl
Contributions: They figured out that DNA replication was semiconservative, meaning that the 2 strands of the DNA molecule separate during replication, then each strand acts as a template for synthesis of a new strand(one new and one old)
How Discovery was made: They conducted an experiment in which the results were consistent with the semiconservative replication process.
This discovery figured out the model of how our DNA splits to give us half of our DNA from mom and half of our DNA from dad.
