-
Friedrich Miescher
Miescher was one of the first scientist to discover that there was a molecule in the nucleus of cells that was made of phosphorus, nitrogen, hydrogen, and oxygen. He didn't call it DNA, but instead called it nuclein. He also discovered that the molecules had a unique ratio of nitrogen to phosphorus. He thought that proteins were the molecules of heredity; even though he wasn't 100% correct, he set the groundwork for future discoveries. He studied pus cells and salmon sperm in his experiments. -
Erwin Chargaff
Chargaff contributed 3 rules involving DNA: Adenine=Thymine percentage, Guanine=Cytosine percentage, & purine= pyrimidine percentage. Chargaff discovered this by looking at the nuclei of cells & isolating the DNA; he then looked at the nucleic acids & separated the purines and pyrimidines using paper chromatography. Next he put the components under ultraviolet light and determined how much of the bases were present. This added to what we know because it helped determine what bases bind together. -
Rosalind Franklin
Franklin was the first scientist to take high resolution photos of crystallized DNA fibers. She took these at Paris using a X-Ray crystallography unit at King's College. By taking these pictures, she discovered the basic dimensions of DNA strands and that phosphates were on the outside of the structure. Her discovery was accepted because her pictures were clear and obvious x-rays of DNA and the pictures helped prove Watson and Crick's model of their DNA model and theory. -
James Watson and Francis Crick
Watson and Crick figured out that DNA was shaped like a three-dimensional double helix held together by hydrogen bases. They discovered this by looking at past scientists' work and data. They came up with an experiment that used pieces of cardboard cutouts to represent nucleotides. During the experiment, they moved the nucleotides around like a puzzle; they fixed the puzzle/came up with their theory after Donohue helped. They were accepted as the first accurate description of the DNA structures. -
Meselson and Stahl
Matthew Meselson and Frankln Stahl were the scientists who discovered how DNA replicated. They did this by culturing bacteria in 15N mediums and then moving them to 14N mediums. They looked at the densities of the bacteria and they found that the DNA molecules had one 15N labeled strand and one 14N labeled strand which proved the semi-conservative replication process. Since the DNA molecule had one original 15N strand and one of the replicated 14N strand, this ruled out the conservative process. -
Hershey and Chase
Alfred Hershey and Martha Chase were the researchers who discovered that DNA is the source of genetic material. They found this by tracking the transfer of proteins and DNA between a virus and a host and seeing that proteins weren't necessary in replicating after inserting genetic material. Their experiment was accepted because the duo did it twice and found that the virus DNA was found in the host and found that the proteins weren't being transferred.
