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P.A. Levene
Determined the basic structure of Nucelotides that make up DNA. Nucleotides are the subunits of DNA. hey are made up of a Five carbon sugar, a phosphate group, and a nitrogenous base. DNA and RNA are the 2 nucleic acids found in living cells.
RNA has the sugar ribose and DNA has the sugar deoxyribose. -
Fredrick Griffith
He studied two strains of bacteria that causes pneumonia. One was sugar coated(Smooth strain) and one was not (rough strain). He did a experiment on mice and found that the smooth strain killed the mouse, while the rough strain did not. But when he made a mixture of both, the mouse died. He removed the live bacteria from the mouse and noticed that a transformation between S bacteria and R bacteria had occured. Now people wanted to identify the transforming substance. -
Oswald Avery
He found a molecule that changed the R strain of bacteria to the S strain. He isolated macromolecules and then exposed the Live R cells to the different macromolecules. He found that when the R cells were exposed to the S strain DNA they changed into S cells. So he said that when the S cells were killed they released DNA and then R Bacteria used the DNA in their cells and changed to the same Bacteria in S cells. -
Erwin Chargaff
He analyzyed the amounts of Adenine, guanine, thymine, and cytosine in DNA. He found out that guanine almost equals the amount of cytosine, also that adenine equals the amount of thymine and created the Chargaff rule C= G and T=A. -
Linus Pauling
He proposed a triple- stranded helix structure for DNA. Phosphate groups faced into the helical core and nitrogenous bases facing out. Thoes three strands interwined to make one helical DNA. But the negative charges of oxygen in each phospate group would repeal one another and the molecule couldnt hold togther. Even though he wote the book on chemical bonding he messsed up. -
Hershey and Chase
In their Experiment they used a virus that attacks bacteria called bacteriophage. This substence was made of DNA and protein and could not replicate themselves. They labled both parts of the virus with a procedure called Radioactive labeling. Their experiment concluded that DNA was what was put into the cell and what provided the genetic information to make new viruses. This showed that DNA was what passed the genetic material through generations in viruses. -
Rosalind Franklin
She produced the X-ray crystallography pictures of DNA. After many differnt jobs she was offered a 3 year research scholarship to set up and improve the X-ray crystallography. She was able to get two sets of high resolution pictures of crystallized DNA fibers. she determined the dimensions of DNA strands and that the phosphates were on the outside of a helical structure. Indicated that DNA was a double helix. -
James Watson and Francis Crick
Watson and Crick meausred the width of the helix and the spacing of the bases. They out toghter their research and built a model of the double helix. Then they wrote a one page letter for the Nature Journal, that talked about a structure for dna and a method of replication for the molecule. Wilmins and Franklin had evidence that supported the structure created by Watson and Crick. -
Maurice Wilkins
His research contributed to the scientific understanding of phosphorescence, isotope separation, optical microscopy and X-ray diffraction. He figured out that he could produce thin threads from this concentrated DNA solution that contained highly oredered arryays of DNA that he could use for the production of x-ray diffraction patterens. He used a group of these DNA threads and made x-ray photographs that showed the long, thin DNA molecule in the sample had a regular crystal like structure.
