DNA as Hereditary Material:

The Transforming Factor

Name: ______

Objective

1. You should be able to use the interactive website at the DNA Learning Center to teach yourself about the experiments conducted by Griffith and then Avery et. al. that demonstrated that DNA was the hereditary material.

Procedure

1. In your assigned computer group enter the website www.dnai.org/index.html by clicking on the “Favorites” menu button after opening Internet Explorer. A page will appear having a picture from the 1950’s of James Watson holding up a model of DNA.

2. Look for the “Timeline” menu button. Click on it and go to the timeline section from 1920-1944 and click on it. Once the figures in that time period load, look for Oswald Avery. Don’t read his biography. Instead click on the link that says “Click to Watch.” Once the Flash multimedia file opens proceed through it and answer the questions below.

Questions

1. What is the name of the bacteria that causes pneumonia?

2. Where are the different places that pneumonia can be grown during experimental studies?

3. Who completed a study on pneumonia bacteria strains in the 1920’s? What were the strains he studied?

4. How were the strains that Griffith studied different from each other? Make sure to include how their structures were different as well as differences in their infectiousness.

5. What did Griffith wonder about that led to his subsequent experiments?

a. What happened when he heat-killed the S-strain? Why is this logical?

b. What happened when he co-injected the heat-killed S-strain and live R-strain? What did Griffith initial expect? What other results associated with this experiment were astonishing to Griffith?

c. What was Griffith’s conclusion regarding this last experiment? Why is this logical?

6. Who did Oswald Avery work with in his experiments? Did they use mice? Explain.

a. What is the lysate that they used for their experiments? What part of the bacteria did it contain?

b. Were they able to observe transformation with just the lysate (without a mouse)? Explain.

c. How did they expand upon Griffith’s experiment to determine what the actual transforming factor was in general?

d. How did they show that the sugar coat from the heat-killed bacteria was NOT the transforming factor?

e. How did they show that the protein from the heat-killed bacteria was NOT the transforming factor?

f. How did they show that the RNA from the heat-killed bacteria was NOT the transforming factor? What did they do first to isolate the nucleic acids?

g. How did they show that the DNA from the heat-killed bacteria WAS the transforming factor?