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CONCLUSION

... The Hershey and Chase experiment concluded that DNA contains genetic material and not protein

Hypothesis Continued

EXPERIMENT

  • They hypothesized that if DNA was genetic material, it would enter the host cell along with the radioactive phosphorus-32, and so radioactive phosphorus- 32 would be found in the pellet of infected bacteria
  • however if the protein contained genetic material radioactive sulfur- 35 would be found in the pellet of the infected bacteria
  • bacteria were allowed to grow during four hours before the phages were introduced
  • when the phages labeled with radioactive sulfur- 35 attached to the bacterium, they injected the DNA but the radioactive coat remained outside of the cell
  • the phages that were then produced in the cell had no radioactivity

HYPOTHESIS

EXPERIMENT CONTINUED

  • since viruses are composed of a protein coat and DNA, Alfred Hershey and Martha Chase used bacteria and bacteriophage to test what molecule contained genetic material
  • They labeled each part of the virus with an elemental isotope
  • radioactive phosphorus- 32 was used to label DNA since phosphorus is present in DNA but is not present in proteins
  • radioactive sulfur- 35 was used to label the protein sections because sulfur is present in amino acids but not in DNA
  • when the phages labeled with phosphorus- 32 were introduced to the bacteria the radioactive phosphorus- 32 labeled DNA entered the cell and was found in the phage produced in to infected bacterium

Alfred Hershey

Born: December 4, 1908

Owosso, Michigan

Died:May 22, 1997

Alfred Hershey was a bacteriologist and geneticist. He received his bachelor's degree in chemistry at Michigan State University in 1930 and his Ph.D. in bacteriology in 1934

Martha Chase

Background

Born: November 30, 1927

Cleveland Heights, Ohio, USA

Died:August 8, 2003 (aged 75)

Martha Chase was a geneticist. She received her bachelor's degree from The College of Wooster. She received her PhD in 1964 from the University of Southern California.

  • In the early twentieth century scientists believed that proteins carried genetic material since they thought that proteins were more complex than DNA
  • however there were experiments conducted that suggested that DNA contained genetic material
  • since scientists were still hesitant about accepting that DNA contained the genetic material Alfred Hershey and Martha Chase decided to conduct an experiment to identify of proteins or DNA carried genetic material

VS.

Alfred Hershey and Martha Chase

By: Katherine Mazo

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