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The Discovery of DNA Itself
Although the actual date is unknown down to the exact day, the Swiss scientist Friedrich Miescher discovered nuclein (Was changed to the term nucleic acid then finally to deoxyriboneucleic acid or DNA) in pus from an infection- he isolated and experimented with the molecule that was pulled away from the nucleus. Although his paper on nuclein was published until 1871, he pushed scientists to recognize the role of nuclein before dying in 1985 from tuberculosis. -
Chargaff's Rule
In 1944, Erwin Chargaff focused his studies into the compositions of DNA. By 1950, he had discovered and published facts that led directly to the allusion of DNA's molecular structure; along with the familiar three rules that became known as Chargaff's rule:
1. The amount of adenine will always equal the amount of thymine.
2. The amount of guanine will always equal the amount of cytosine.
3. The amount of pyrimidines will always equal the amount of purines. -
The recognition that DNA is hereditary material - not proteins
The scientists A.D Hershey and Martha Chase experimented with a virus and found that when bacteriophages were allowed to infect nonradioactive bacteria, all the infected cells became radioactive and the radioactivity was passed down to the next generation of bacteriophages. However, when the bacteria were infected with bacteriophages and the virus coats were removed, little to no radioactivity could be detected in the infected cells. They found out that DNA, were the source of genetic material. -
The Discovery of DNA's structure
Watson, Crick, Rosaline Franklin, and Maurice Wilkins were all working to find DNA's structure. In 1951, Watson attended a lecture by Franklin on her work. Wilkins ended up showing Watson the first picture of DNA. After being shown that image and being told a multitude of other things, Watson and Crick took a huge step by saying DNA was made up of two strands, not one. After learning about Chargaff's rule in 1952, they put the pieces together and founded the double helix we all know today. -
Testing the theory of DNA replication
Meselson and Stahl tested the hypothesis of DNA replication. They took bacteria and cultured it in 15N so the DNA synthesized would have heavy density. Then they grew more bacteria in 14N, giving that DNA a lighter density. Meselson and Stahl isolated the DNA at different times according to the DNA replication process, only to find out that both 15N labeled strands bonded with both 14N labeled strands, resulting in an intermediate density in both DNA.
