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Discovery of Nucleic Acids - Frederich Miescher
Nucleic acid was discovered. He isolated the genetic material from white blood cell nuclei. He noted it had an acidic nature and called it nuclein. -
Discovery of DNA Components - Phoebus Levene - (1869 - 1940)
He discovered all of the components of DNA. He also defined the unit, and the base which he called a nucleotide.
He proposed a structure of DNA but it turned out to be incorrect. -
Demonstrated Bacterial Transformation - Frederick Griffith- (1879 - 1941)
He discovered the genetic phenomenon called bacterial transformation but could not find an explanation.
He identified two forms of the bacteria that cause pneumonia: virulent (smooth) and non-virulent (rough). -
Triple helix - Linus Pauling - (1901 - 1994)
Linus Pauling, discovered the structure of the alpha helixes and the beta sheets in proteins, he came up with the triple helix model, again, with the phosphates on the outside. That turned out to be incorrect. -
Maurice Wilkins (1916 - 2004) Rosalind Franklin (1920 - 1958)
Franklin obtained an X-ray diffraction photograph that revealed the helical structure of the DNA molecule. Maurice Wilkins took the photos from his desk and presented them to Watson and Crick. They established the hypothesis of the "double helix". These discoveries made it possible to understand molecular biology and genetic principles. -
Oswald Avery (1877 - 1955), Colin MacLeod (1909 - 1972) and Maclyn McCarty (1911 - 2005)
They determined the cause of the transformation (in 1944) of the Griffith’s experiment through another experiment.
They showed that it was the DNA the hereditary material of bacteria and the responsible for the transformation. -
Double helix - James Watson and Francis Crick
They described DNA as a double helix with sugars and phosphates at the center and the nucleobases facing the outside.
Later this model was shown to be incorrect. -
Counting Nucleobases - Erwin Chargaff - (1952)
Chargaff studied different organisms and he measured the amounts of the four bases (A, T, G, C) watching that these didn't vary much. The amount of the nucleotides A - T, and G - C are always balanced. -
Hershey and Chase Experiments - (1952)
From their experiments it was concluded that the DNA component of the bacteriophage is injected into the bacterial cell while the protein component remains outside. However, it is the injected component, DNA, that can direct the formation of new virus particles entirely. This is further proof that genes are DNA. -
Structure for Deoxyribose Nucleic Acid - Watson J.D and Crich F.H.C.