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Miescher: First Discovery of DNA
At first, Miescher focused on the various types of proteins that make up the leucocytes, as proteins were considered to be the most promising targets for understanding how cells function. Miescher noticed that a substance precipitated from the solution when acid was added and dissolved again when alkali was added. He had obtained a crude precipitate of DNA. -
Joseph Thomson: The Electron
In 1897 the British physicist Joseph John Thomson discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, an area being investigated by numerous scientists at the time. Thomson suggested a model of the atom as a sphere of positive matter in which electrons are positioned by electrostatic forces. -
Garrod: Idea of genetic
Based on discussions with Mendel advocate William Bateson, Garrod deduced that alkaptonuria is a recessive disorder. He believed that diseases were the result of missing or false steps in the body's chemical pathways. Archibald Garrod was the first to connect a human disorder with Mendel's laws of inheritance. He also proposed the idea that diseases came about through a metabolic route leading to the molecular basis of inheritance. -
Griffith
Griffith's experiment was an experiment done in 1928 by Frederick Griffith. It was one of the first experiments showing that bacteria can get DNA through a process called transformation. Griffith used two strains of Pneumococcus. These bacteria infect mice. He used a type III-S (smooth) and type II-R (rough) strain. The III-S strain covers itself with a polysaccharide capsule that protects it from the host's immune system. This means that the host will die. -
Avery: DNA Transformations
In 1944, experiments by Oswald T. Avery showed that a nucleic acid, deoxyribonucleic acid (DNA), known to be ubiquitous in organisms, was the chemical basis for specific and apparently heritable transformations in bacteria. Deoxyribonucleic acid (DNA) plays a central role in determining specific characteristics in the course of reproduction. -
Chargaff: Nucleotide Count
Erwin Chargaff was the first to accurately measure nucleotide amounts in DNA. Chargaff established that the ratio of purines to pyrimidines was 1. Chargaff’s base ratios were given a stereochemical interpretation as “base pairings” as part of the double-helix structure proposed by Watson and Crick in April 1953. -
Hershey and Chase
When bacteriophages containing 32P (radioactive), were allowed to infect nonradioactive bacteria, all the infected cells became radioactive and, in fact, much of the radioactivity was passed on to the next generation of bacteriophages. However, when the bacteria were infected with bacteriophages labeled with 35S, and then the virus coats removed practically no radioactivity could be detected in the infected cells. -
Franklin and Wilkins
She used two different fibers of DNA, one more highly hydrated than the other. From this she deduced the basic dimensions of DNA strands, and that the phosphates were on the outside of what was probably a helical structure. The data confirmed the 3-D structure. In 1953, both Wilkins and Franklin published papers on their X-ray data in the same Nature issue with Watson and Crick's paper on the structure of DNA. -
Watson and Crick
DNA pairing always occurs between A & T, and C & G. James Watson and Francis Crick realized that these pairing rules meant that either strand contained all the information necessary to make a new copy of the entire molecule, and that the order of bases might provide a "genetic code".
