Chapter 13

Question 1

HPV (Human Papillomavirus)

Answer 1

Non-enveloped dsDNA

Question 2

Smallpox

Answer 2

Enveloped dsDNA

Question 3

Norovirus

Answer 3

Non-enveloped ssRNA (+ strand)

Question 4

Rubella

Answer 4

Enveloped ssRNA (+ strand)

Question 5

Rabies, Ebola, Mumps and Measles, Influenza

Answer 5

Enveloped ssRNA (- strand)

Question 6

Hepatitis B

Answer 6

Enveloped DNA (reverse transcribing)

Question 7

HIV

Answer 7

Enveloped RNA (reverse transcribing)

Question 8

Lytic Phage Infections

Answer 8

1. Attachment: Phages attach to specific receptors
2. Genome Entry: Genome is transferred from virus to bacteria
3. Synthesis: Genome transcribed, proteins and other components synthesized, host DNA degraded
4. Assembly: All the components are assembled into new viruses within the cell
5. Release: The cell lyses and all the new viruses are released

Question 9

Temperate Phage Infections

Answer 9

These viruses can go straight to a lytic phage infection process, or, halfway through go to a lysogenic infection and then back to the lytic infection.

1. Attachment
2. Genome Entry: The injected linear phage’s DNA joins at the ends to become circular
3. This DNA joins with the host’s chromosomes and integrates. It’s called the prophage
4. The cell divides to breed two new cells with the viruses DNA
5. The phage’s DNA is excised (split) from the prophage in all the cells that were made
6. Then continues the lytic cycle by synthesizing components, and lysing to release new viruses

A repressor can prevent excision, so the virus stays in the lysogenic state and just keeps multiplying. This is normally the case. Only 1 in 10,000 divisions are excised

Question 10

Phage Induction

Answer 10

Part of Temperate Phage Infections.
If the DNA of the host happened to be damaged, then obviously the host’s SOS repair system turns on. Consequently, this SOS system activates a protease. The protease destroys the repressor that keeps the phage DNA multiplying with the host chromosome. Now the phage DNA can be excised, and then the cell lysed from the lytic cycle for the virus to escape

Question 11

Filamentous Phages

Answer 11

The filaments attach to the f pilus in the cell and inject its ssDNA. They replicate and synthesize capsomeres which embed into the membrane, Other proteins create pores. Then the new DNA is excreted, getting coated with the capsomeres on the way out, becoming nucleocapsids

Question 12

Generalized Transduction

Answer 12

Happens when phage isn’t packaged correctly in the host. When the phage degrades the host chromosome, some of the fragments get mistakenly packaged in the phage head

Question 13

Specialized Transduction

Answer 13

Excised viral DNA isn’t properly excised; a fragment is switched with the host DNA. When cell lyses and virus is released, it’s defective

Question 14

Animal Virus Replication

Answer 14

1. Attachment
2. Penetration: Either by fusion or endocytosis, but non-enveloped viruses can’t fuse
3. Synthesis: Either from DNA, RNA, or Reverse Transcribing
4. Assembly
5. Release