Frederick Griffith
Examine the picture below and the animation at the following link
http://www.youtube.com/watch?v=885BkHWPQik
1. How does information resulting from Griffith’s experiments with Streptococcus
pneumoniae support the idea that a heritable material (the identity of which was
unknown in 1928) transformed living, nonpathogenic “R” bacteria into pathogenic “S”
bacteria?
Analysis:
1. Form inferences about each of Griffith’s four experiments.
2. Draw conclusions regarding each of the two bacterial strains from their
experimental inferences.
Hershey – Chase
Examine the picture below and the animation at the following link
http://www.youtube.com/watch?v=X1cd68YkVdM
1. Is DNA or protein the genetic material of phage T2?
2. How does evidence resulting from the Hershey–Chase experiments support that
DNA, not protein, is the heritable material?
Analysis
1. Why did they use radioactive sulfur in experiment 1 and radioactive phosphorus in
experiment 2?
2. Discuss the results of the Hershey–Chase experiments with T2. Where was
radioactive sulfur found at the end of experiment 1? Where was it found at the end
of experiment 2?
3. Draw conclusions from the results assuming that the material (DNA or protein) that
was found in the bacterial cells is, in fact, the genetic material.
4. Based on the Hershey–Chase experiments, is it reasonable to assume that Griffith’s
“transforming factor” was DNA, not protein? Why or why not? What is the
connection between the two experiments?