1. Objectives 12.1 Identifying the Substance of Genes -Summarize the process of bacterial transformation. -Describe the role of bacteriophages in identifying genetic material. -Identify the role of DNA in heredity.

2. Lesson Overview Lesson Overview Identifying the Substance of Genes What do they mean by Bacterial Transformation??? To find out Griffith isolated two different strains of the same bacterial species; only 1 caused pneumonia. Disease-causing bacteria = S strain Harmless bacteria = R strain Live R and dead S strains were mixed and the R strain turned deadly:-/ He called this process transformation, because one type of bacteria was changed by another.

3. Lesson Overview Lesson Overview Identifying the Substance of Genes What caused Transformation??? Avery and his team extracted a mixture of molecules from the heat-killed bacteria and treated it with enzymes that destroyed proteins, lipids, carbohydrates and RNA. Transformation STILL occurred.

4. Lesson Overview Lesson Overview Identifying the Substance of Genes Only DNA is left… Avery’s team repeated the experiment using enzymes that would break down DNA. When they destroyed the DNA in the mixture, transformation did NOT occur.

5. Lesson Overview Lesson Overview Identifying the Substance of Genes The Hershey-Chase Experiment American scientists Alfred Hershey and Martha Chase studied a bacteriophage that was composed of a DNA core and a protein coat. They wanted to determine which part of the bacteriophage entered the bacterial cell.

6. Lesson Overview Lesson Overview Identifying the Substance of Genes The Hershey-Chase Experiment DNA They labeled the bacteriophage protein and DNA with radioactive substances and found that the hereditary material injected into the cell was DNA, not protein.

7. Lesson Overview Lesson Overview Identifying the Substance of Genes The function of DNA… 1. Storing information; 2. Copying information; 3. Transmitting information.