-
Miescher
He was assigned to do research on white blood cells. Through this he discovered the nuclein. He found an easy way to isolate white blood cells. This way was to get it from pus. He collected bandages from a nearby clinic and washed off the pus. He washed the pus in chemicals that extracted the nuclein. We now call the nuclein Nucleic Acid. Miescher isolated something no one had ever seen before from the nucleus of the cells. -
Chargaff
He came up with what we now call Chargaff's Rule. He took DNA from different organisms and isolated it. He then measure how much of each of the nitrogenous bases were in each organism. He found that even though adenine and thymine don't equal each other, they are close. The same is true for Cytosine and Guanine. Before this, we didn't know that the bases followed the same pattern no matter the species. We still don't know why this occurs, but chargaff helped us to know that it does occur. -
Franklin
She is credited with finding the helix shape of DNA, the fact that it has 2 strands, and that the nitrogenous bases are near the center of the molecule. Her contribution was made through observations and research. She used a method called X-ray diffraction. She took large amounts of DNA and stretched the fibers in a thin glass tube. Then, she aimed an X-ray beam at the concentrated DNA samples. The images she came up with from this didn't reveal the structure, but gave clues that helped others. -
Hershy & Chase
They confirmed previous research that genetic material found in viruses is not protein, but DNA. They conducted experiments to reach this conclusion. They grew viruses containing radioactive isotopes such as phosphorus-32 and sulfur-35. Protein doesn't have any phosphorus and DNA doesn't have any sulfur. These served as markers. Depending on which one it had, DNA or protein, that is what radioactive isotope would enter the virus. -
Hershey & Chase (continued)
Before this, Avery's researched proved that DNA stores and transmits genetic information from 1 generation to the next. They confirmed that genetic material is found in genes in all living things. -
Watson & Crick
They contributed the double-helix model. They discovered that this was how DNA looked by first building 3-D models out of cardboard and wire. They then stretched and twisted in attempt to discover properties of DNA. However, that did not work. They discovered Franklin's work and built a model based on it. Before Watson & Crick we didn't have an accurate model of DNA. -
Melson & Stahl
They worked together to conduct experiments that led to the semi-conservative model of how DNA replicates itself. They met through a class Watson and Crick were teaching. They invented a new theory called the density gradient centrifugation. This is where molecules are separated by centrifugal force based on their densities. Before this people were unsure of how DNA replicated. Through experiments they proved that each DNA strand is half new and half old DNA. The new DNA is new nucleotide bases.
