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Alfred Hershey and Martha Chase
Transcript of Alfred Hershey and Martha Chase
Martha Chase Alfred Hershey Bacteriophage, "Eater of Bacteria": DNA and Protein are conveniently structurally different! Identifying the Genetic Material Their findings led Watson and Crick to study and determine the structure of DNA Sources Martha Chase Felix d'Herelle discovered bacterial viruses in 1917 They used radioactive isotopes of sulfur or phosphorous to track parts of the bacteriophage after it infected a bacterium http://www.nobelprize.org/nobel_prizes/medicine/laureates/1969/hershey-bio.html
Alfred Hershey Born on December 4, 1908 Studied at Michigan State College;
received B.S. in 1930 and Ph.D. in 1934 Died on May 22, 1997 Martha Chase Born in Cleveland, OH in 1927 Graduated from the College of Wooster in 1950 Bacteriophages have only DNA and Protein The virus takes over and uses a bacterium to create more viruses Bacteriophages are extremely simple! So Hershey and Chase set out to determine which part of the bacteriophage served to take over the bacterium it infected WHY DID THIS MATTER TO HERSHEY AND CHASE? Only the DNA or the protein could hold the genetic material DNA PROTEIN DNA Protein No sulfur Large amount of phosphorous Sulfur (contained in side chains of certain amino acids) Very little phosphorous Present in bacteriophage! Once the bacteriophage had infected the bacterium, the culture was placed in a blender so that the bacteriophage capsules fell off the bacteria Sulfur would be incorporated into protein and phosphorous into DNA This method allowed the location of DNA and protein to be tracked easily The culture was run through a centrifuge to separate the different parts They knew that the bacteriophage was composed of a protein shell with DNA inside Bacteria cells fell to the bottom; loose phage parts remained in the liquid above In cultures with radioactive sulfur (tracking protein), the radioactive isotopes were located in the water that suspended loose phage parts In cultures with radioactive phosphorous (tracking DNA), the radioactive isotopes were located in the bottom with the bacteria cells DNA directed the takeover of the infected bacterium! The offspring of the phosphorous labeled bacteriophages (tracking DNA) also contained radioactive phosphorous in their DNA DNA alone was the material of heredity! Prior to Hershey and Chase proving that DNA carried genetic information, it was usually believed that protein carried the information Alfred Hershey was awarded the Nobel Prize in Physiology or Medicine in 1969, but Martha Chase was left out Hershey and Chase chose to work with a bacteriophage known as T2, which infects E. Coli Died of pneumonia on August 8, 2003 Pictures http://www.xtimeline.com/evt/view.aspx?id=397761