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Fredrick Griffith
When Griffith was studying DNA he tested two types of bacterium strains. The R-strain and the S-strain. He found that the S-strain killed the mice and the R-strain didn't. He also injected the mice with the a S-strain that had been killed by the heat which didi not kill the mice. But when the dead S-strain was mixed with the R-strain it killed the mice. Griffith came to the conclusion that something in the S-strain transferred to the unharmless R-strain making it deadly. -
Oswald Avery
A team led by Oswald Avery inactivated substances in the S-strain bacteria. Then they killed the S-strain bacteria and mixed the remains with live R-strain bacteria. When they inactivated proteins the R-strain became deadly. Which means that proteins are not genetic material. But when the researches inactivated DNA in the S-strain the r-strain remained harmless. Which means DNA is the genetic material. -
Erwin Chargaff
Chargaff thought there had to be more to repetitve tetranucleotide blocks. First he isolated the DNA from different organisms and measured the level of each of the four nitrogenous bases. The results of the adnenine and the thymine were extremly close. So was guanine and ctyosine. This proves that Levene's theory is incorrect. -
rosalind franklin
In 1951 franklin was hired to improve the x-ray crystallography at a college. So she made DNA x-ray diffraction patterns She calculated the basic demensions of a DNA molecule. The information was eventually used to solve the 3-dimensional structure of DNA. -
Alfred Hershey and Martha Chase
Hershey and his collegue Chase wanted to determine what caused the transformation of bacteria into a bacteriophage producing factory. Bacteriophage are viruses that specifically attack and infect bacteria. Could it be that suggested in Avery's work that bacteriophage DNA was a "transforming principle". So first they used sulfur to selectivley label phage DNA and protein. throught their very long experiment they found that DNA is the genetic material. -
Watson and Crick
Watson and Crick were the first to publish an accurate model of the DNA molecule. After Avery's lnadmark paper they new DNA had to be intellegent. They knew it made more sense that the nucleotides changed. that way information can be coded into the DNA sequence.
