AP Biology 12Concept 1 continued: Analyzing components

and reproduction cycles of viruses

Please refer to: Chapter 19 in Campbell

pg 134-136 in Holtzclaw

Practice Questions:Holtzclaw: #2,10

p.143,144Campbell: #1,2 (19.1)

p. 384#1, 2, 3, 4 (19.2) p. 390

#1,2,3,8 p. 395,

Learning Intentions

You must know:The components of a virusThe differences between lytic and lysogenic

cycles

Can you find the viruses?

What are the viruses infecting?

What does this bacteriophage virus remind you of?

How were viruses first discovered?

Waaaaay smaller than bacteria!

Tobacco mosaic disease

How does this experiment support the idea of viruses?

Discuss: Are viruses alive or dead? Why? What defines a virus? What defines life?

Try This!

Which of the following is not a property of life shared by prokaryotic cells, eukaryotic cells, and viruses?

A. nucleic acids used to store hereditary information

B. order and complexity in arrangement of biological molecules

C. the ability to process energy through metabolic reactions

D. the capacity to evolve

Try This!

Which of the following is not a property of life shared by prokaryotic cells, eukaryotic cells, and viruses?

A. nucleic acids used to store hereditary information

B. order and complexity in arrangement of biological molecules

C. the ability to process energy through metabolic reactions

D. the capacity to evolve

Try This! Viruses:“a kind of borrowed life”

Classify each statement as TRUE or FALSE, and identify which statement supports the view of most biologists that viruses are nonliving.

A. Viruses are two-dimensional, rather than three-dimensional.

B. The viral genome may be single- or double-stranded. C. Viruses are obligate intracellular parasites. D. An isolated virus is unable to replicate its genes or

regenerate ATP.

Try This! Viruses:“a kind of borrowed life”

Classify each statement as TRUE or FALSE, and identify which statement supports the view of most biologists that viruses are nonliving.

A. Viruses are two-dimensional, rather than three-dimensional. FALSE

B. The viral genome may be single- or double-stranded. TRUE

C. Viruses are obligate intracellular parasites. TRUED. An isolated virus is unable to replicate its genes or

regenerate ATP. TRUE

What is a virus made of?

Genetic material: single or double stranded DNA or single or double stranded RNA

Protein shell: capsidSome viruses also have

viral envelopes from membrane of host cells

Compare the structure of these two viruses:

Compare the structure of these three viruses:

Try This!

Bacteriophages were grown in a medium containing radioactive sulfur (35S) and radioactive phosphorous (32P), which are incorporated into proteins and DNA, respectively. If these phages were used to infect a bacterial culture, which isotope would be detected within the infected bacteria?

A. 35SB. 32PC. bothD. neither

Try This!

Bacteriophages were grown in a medium containing radioactive sulfur (35S) and radioactive phosphorous (32P), which are incorporated into proteins and DNA, respectively. If these phages were used to infect a bacterial culture, which isotope would be detected within the infected bacteria?

A. 35SB. 32PC. bothD. neither

How do viruses replicate?

Overall: Simplified Viral Reproduction (Campbell Online)

How do viruses replicate?

Bacteriophage: Lytic vs lysogenic cycles (Campbell) (Campbell)

How does a virus replicate?

Retroviruses (Campbell))

Use the enzyme reverse transcriptase

Example: HIV

Try This!

AZT is a nucleoside analog used to treat HIV infections. It is a thymine (T) nucleoside with an azide group instead of the hydroxyl group found in typical thymine nucleosides. Which step does AZT hamper in the reproductive cycle of the HIV virus?

A. entry into the cellB. reverse transcription of DNA from RNAC. transcription of RNA from proviral DNAD. viral assembly within the cell

Try This!

AZT is a nucleoside analog used to treat HIV infections. It is a thymine (T) nucleoside with an azide group instead of the hydroxyl group found in typical thymine nucleosides. Which step does AZT hamper in the reproductive cycle of the HIV virus?

A. entry into the cellB. reverse transcription of DNA from RNAC. transcription of RNA from proviral DNAD. viral assembly within the cell

Viroids and Prions: the really little guys

Viroids – circular RNAMostly affects plants

Prions – misfolded, infectious proteinExample: Mad Cow

Try This!

Identify all correct statements.A. Unlike viruses, viroids do not encode proteins.B. Unlike viruses, the genetic material of a viroid

is RNA.C. Unlike viruses, prions are infectious proteins.D. Unlike viruses, prions do not include any

nucleic acids.

Try This!

Identify all correct statements.A. Unlike viruses, viroids do not encode proteins.B. Unlike viruses, the genetic material of a viroid

is RNA.C. Unlike viruses, prions are infectious proteins.D. Unlike viruses, prions do not include any

nucleic acids.

Beautiful viral animationHepatitis C virus

Viral structures

Discovery Channel - Emerging Diseases (CD-Rom)

Learning Intentions

You must know:The components of a virusThe differences between lytic and lysogenic

cycles

Try These:

1. Explain how capsids and envelopes are formed

2. Distinguish between the lytic and lysogenic reproductive cycles

3. Explain why viruses are obligate intracellular parasites

4. Describe the reproductive cycle of an HIV retrovirus

5. Describe three processes that lead to the emergence of new diseases

6. Describe viroids and prions