-
Frederick Griffith
Frederick Griffith experimented with mice and pneumonia bacteria. He injected two different strains of bacteria, Rough (R) and Smooth (S), into the mice, The S bacteria killed the mice, while the R was harmless. S bacteria that was killed with heat was also harmless to the mice. When combining the heat killed S bacteria and the R bacteria, the mice died. Griffith named the process in which the killed S bacteria passed the disease carryihng ability to the harmless bacteria transformation. -
Oswald Avery
Oswald repeated Griffith's work to determine which molecule was most important in causing the transformation. He created an extract of the heat-killed bacteria. It was treated with enzymes that broke down different molecules. They tested it again, and the transformation still occured. They repeated the experiment, with enzymes that broke down DNA. The transformation did not occur. From the experiments it was discovered that DNA stores and transmits genetic information. -
Erwin Chargaff
Erwin Chargaff found that the percentages of guanine (G) and cytosine (C) bases were almost equal in samples of DNA. The same was true for adenine (A) and thymine (T). Chargaff's rules came from the observation (A)=(T) and (G)=(C). -
Rosalind Franklin
Rosalind Franklin used X-ray diffraction to study the structure of DNA. She recorded the scattering patterns of the x-ray on film to determine patterns. The pattern itself does not show the structure of DNA, but gives many clues that suggest the structure. -
Alfred Hershey and Martha Chase
They studied viruses. They grew viruses incultures containing radioactive isotopses of phosphorus -32 and sulfur-35, to determine if the protein coat or the DnA core infected the cell. Most of the radioactivity was from phosphorus, the marker found in DNA. They discovered that the genetic material of the bacteriophage was DNA. -
Watson an Crick
Watson and Crick collaborated in an attempt to build a model to show the structure of DNA. Weeks after seeing Franklins work, they completed their model and published their results. Their model was a double helix.
