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Name
Date
Period
HBiology
DNA Experiments
12.1 Identifying the Substance of Genes
Directions: Read over the following early DNA experiments and draw conclusions based on the information
given.
Experiment #1 ______________________
Purpose: The purpose of this experiment is to determine if genetic information can be transferred from
one organism to another.
Procedure:
1. Inject mice with Pneumococcus bacteria strain S.
2. Inject mice with Pneumococcus bacteria strain R.
3. Inject mice with heat-killed Pneumococcus bacteria strain S.
4. Inject mice with heat-killed Pneumococcus bacteria strain S mixed with normal strain R bacteria.
Results:
Pneumococcus Strain
Mouse Health
Strain R
No pneumonia development  mice healthy
Strain S
Mice developed pneumonia  death of mouse
Heat-killed strain S
No pneumonia development  mice healthy
Heat-killed strain S + Living
Mice developed pneumonia  death of mouse
Strain R
Conclusion:
Transformation -
Experiment #2 ______________________
Purpose: The purpose of this experiment is to determine what material is responsible for transferring
genetic information.
Procedure:
1. Created a “juice” of heat-killed bacteria.
2. Treated juice with enzymes to kill potential genetic information.
3. Observed if genetic information was passed on to other healthy bacteria.
Results:
Enzyme Kills:
Lipids, carbohydrates, proteins
RNA
DNA
Result
Genetic information transferred
Genetic information transferred
Genetic information not transferred
Conclusion:
Experiment #3 ______________________
Background information: Bacteriaphages are viruses that infect bacteria by injecting their genetic
material and forcing the bacteria to reproduce viruses instead of their own genetic material. The phage
is very simplistic and is composed of only a protein covering and a small piece of DNA inside the protein
covering.
Purpose: The purpose of this experiment was to determine what material is responsible for transferring
genetic material.
Procedure:
1. Mix radioactive bacteriaphages with bacteria; phages will inject their material into bacterial cells
for copying and reproduction.
 DNA labeled with radioactive Phosphorus
 Protein coat labeled with Sulfur
2. Blend bacterial cells in blender to separate bacterial cell parts from phages and each other.
3. Measure radioactivity in the bacterial cells.
Results:
Bacteria found to contain radioactive PHOSPHORUS inside after being fractionated and centrifuged
to separate them from the phages.
Conclusion: