Viral Replication L18

Question 1

Describe a viral genome.
Coding molecule?
Base length?
Associated with?

Answer 1

• Nucleic acid genome (DNA or RNA)
• 3000 – 1.2 million bases
• Associated with proteins, sometimes enveloped

Question 2

True or false? Viruses evolve slowly.

Answer 2

False. Viruses evolve rapidly.

Question 3

Starting with Entry, name the cycle of viral infection.

Answer 3

• Entry
• Primary site replication
• Spread within host
• Shedding
• Transmission

Question 4

What does viral entry into host cell depend on?

Answer 4

Interaction between viral surface protein and host cell surface protein = VIRUS RECEPTOR

Question 5

What do viruses require for biosynthesis?

Answer 5

• Host ribosomes
• Enzymes
• Precursors

Question 6

Name the 3 parts of viral biosynthesis.

Answer 6

• Genome replication
• mRNA synthesis
• Translation

Question 7

How many different classes of virus have been identified?

What are the classes based upon?

Answer 7

7.

Based on 7 different patterns of replication and transcription .

Question 8

Which is the only virus not transcribed and replicated in the nucleus?

Answer 8

The pox virus.

Question 9

True or false? DNA virus genomes can be replicated and transcribed by host polymerases.

Answer 9

True.

Question 10

True or false? RNA virus genomes can be replicated and transcribed by host polymerases.

Answer 10

False. RNA virus genomes cannot be replicated and transcribed by host polymerases.

Question 11

What is the difference between positive and negative stranded RNA viruses?

Answer 11

• A positive stranded RNA virus’s genome can be directly translated
• A negative stranded RNA virus must synthesise coding strand (+ve) before translation

Question 12

What is the classification system used to classify viruses called?

Answer 12

The Baltimore’s Classification.

Question 13

Which viruses? Their genomes encode Reverse Transcriptase.

This allows them to synthesise DNA from an RNA template.

Answer 13

Retroviruses and Hepadnaviruses.

Question 14

What are the functions of the proteins encoded by the virus genome?

Answer 14

• Replication of the genome
• Package the genome into virus particles
• Alter the metabolism of the infected cell

Question 15

Name the 5 basic structural forms of viruses.

Give examples.

Answer 15

1. Naked icosahedral
   - e.g. poliovirus, adenovirus, rhinovirus
2. Naked helical
   - e.g. tobacco mosaic virus
3. Enveloped icosahedral
   - e.g. herpes virus
4. Enveloped helical
   - e.g. measles virus
5. Complex
   - e.g. poxviruses

Question 16

In what 2 ways can viruses be released from the host cell?

Answer 16

• By cell lysis

- By budding