1. Warm-Up (12/01)
On the piece of white paper from the back, answer the following question.
Name
Date
Period
How did the Hershey-Chase experiment prove that DNA is the heritable molecule of genes?

2. Viruses infect cells by injecting genetic material
For example, a virus infecting a bacterium.

3. Make more proteins and DNA
The Lytic Cycle
DNA
proteins
Make more proteins and DNA
Lysis

4. The Lytic Cycle ∴, many generations turn over quickly.
Viral replication happens very quickly.
∴, many generations turn over quickly.
∴, viruses accumulate mutations and new phenotypes very quickly.
Lysis

5. Critical Thinking Question #1
Discuss this question with your partner and write or represent it. I will call on three people to share their partners’ answers.
Draw a virus infecting a cell with its DNA being injected in, the host cell’s transcription and translation machinery producing RNA and protein, respectively, and new viruses being assembled from the proteins. Draw the cell bursting after this process is repeated many times and many viruses leaving the cell. Represent mutations on some of these new viruses to show genetic variation introduced as a result of viral replication. Title your drawing “The Lytic Cycle.”

6. The Lysogenic Cycle Host cell replicates its own + viral DNA
“integrates” into host cell DNA

7. The Lysogenic Cycle
Transformed bacteria can have new phenotypes, such as becoming more pathogenic.
Similar viruses which infect the same cell can recombine or “cross over” their DNA.

8. Critical Thinking Question #2
Discuss this question with your partner and write or represent it. I will call on three people to share their partners’ answers.
Draw a virus infecting a bacterium with its DNA being injected in, and the DNA integrating into the host cell’s genome. Show how the host bacterium has new properties because of the new proteins being produced. Title your drawing “The Lysogenic Cycle.”

9. Closure
On the piece of white paper from the back, answer the following question:
Name
Date
Period
Explain how viruses are able to evolve very rapidly.
Scale 1 – 10