FR Chap 16 Viruses

Question 1

What are three basic shapes of viruses?

Answer 1

1) Helical virions
2) Polyhedral shape
3) Complex virus shape

Question 2

Describe three things that categorize viruses

Answer 2

Helical virions are set up like a tube. The protein coat winds up like a garden hose around the core.
Polyhedral shape. This shape group includes the classic virus shape that looks like a dodecahedron.
Complex virus shape. Geometric head & long legs.

Question 3

Name two major reasons viruses are considered non-living.

Answer 3

Not made of cells
They can’t reproduce on their own
They don’t respond to anything
No working parts

Question 4

Describe the Lytic Virus cycle?

Answer 4

In the lytic cycle, the phage attaches to the host cell & injects its DNA. The host cell’s enzymes and synthesis machinery makes copies of the viral DNA and viral proteins. The viral proteins and nucleic acids then assemble themselves inside the host cell, making many copies of the original infecting virus. The host cell then bursts open, releasing hundreds of new viruses. These offspring infect new host cells & repeat the cycle.

Question 5

Describe the Lysogenic Virus Cycle?

Answer 5

In the lysogenic cycle, a virus injects ints genes into the host. The virus DNA then adds itself directly to the host cell’s DNA. Each time the host cell reproduces, the viral DNA is copied along with the host’s DNA. Occasionally, the viral DNA separates from the host DNA & starts a lytic cycle.

Question 6

Retrovirus? Provide an example of one.

Answer 6

Retrovirus - member of a group of viruses such as HIV that carry reverse transcriptase, which catalyses the synthesis of DNA from an RNA template.