1. Warm-Up (12/02)
On the piece of white paper from the back, answer the following question.
Name
Date
Period
Explain the difference between the lytic cycle and the lysogenic cycle. What do they both have in common?

2. reverse transcriptase
Retroviruses
Normal viruses contain DNA and inject that DNA into a host cell.
Retroviruses contain RNA.
RNA
injected RNA
reverse transcriptase
DNA
RNA
(gene expression)

3. reverse transcriptase
Retroviruses
Normal viruses contain DNA and inject that DNA into a host cell.
Retroviruses contain RNA.
RNA
injected RNA
reverse transcriptase
DNA
If I wanted to target HIV fight it without hurting human enzymes, which enzyme should I target?
RNA
(gene expression)

4. HIV ∴, it evolves very rapidly.
HIV goes through the lytic cycle and acquires mutations very rapidly.
∴, it evolves very rapidly.
“retroviral” drugs

5. HIV ∴, it evolves very rapidly.
HIV goes through the lytic cycle and acquires mutations very rapidly.
∴, it evolves very rapidly.
“retroviral” drugs

6. HIV ∴, drug resistance can happen easily.
HIV goes through the lytic cycle and acquires mutations very rapidly.
∴, drug resistance can happen easily.
“retroviral” drugs

7. HIV ∴, drug resistance can happen easily. ∴, it evolves very rapidly.
HIV goes through the lytic cycle and acquires mutations very rapidly.
∴, drug resistance can happen easily.
∴, it evolves very rapidly.
“retroviral” drugs

8. 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.
Explain how HIV strains can become resistant to anti-retroviral drugs.

9. What makes HIV so bad? DNA RNA injected DNA injected RNA DNA RNA RNA
Host cell machinery, including error-checking enzymes
DNA
Host cell machinery, including error-checking enzymes
RNA
(gene expression)
RNA
(gene expression)

10. What makes HIV so bad? DNA RNA injected DNA injected RNA DNA RNA RNA
Mutations!
Mutations!
injected DNA
injected RNA
No error checking!
Host cell machinery, including error-checking enzymes
DNA
Host cell machinery, including error-checking enzymes
RNA
(gene expression)
RNA
(gene expression)

11. 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 the lytic cycle of the HIV virus (as you did yesterday), showing reverse transcriptase. Also indicate the point at which the genetic material can acquire mutations much more rapidly than DNA-based viruses.

12. Closure
On the piece of white paper from the back, answer the following question:
Name
Date
Period
Why do retroviruses evolve more rapidly than DNA-based viruses?
Scale 1 – 10