Chapter 19

Question 1

What did Beijerinck conclude?

Answer 1

That it needed host to reproduce

Question 2

What are the 2/3 parts of viruses?

Answer 2

1. Genome
2. Capsid
3. Envelope

Question 3

What are the components of a viral envelope and where do they originate from?

Answer 3

Membrane proteins/phospholipids from host cell;

Proteins and glycoproteins of viral origin

Question 4

What are bacteriophages?

Answer 4

Viruses that infect bacteria strictly

Question 5

What does Phage T4 infect?

Answer 5

E. Coli

Question 6

Host range?

Answer 6

Range of types of cells a certain type of virus can infect

Question 7

When does viral infection begin?

Answer 7

When virus binds to host cell

Question 8

What are the 3 mechanisms of genome entry?

Answer 8

1. Injection from tail
2. Endocytosis
3. Fusion of envelopes

Question 9

What is the method of genome entry for phages?

Answer 9

Injection from tail

Question 10

What are capsids made up of?

Answer 10

Capsomeres

Question 11

What type of phage undergoes the lytic cycle?

Answer 11

Virulent phage

Question 12

What type of phage undergoes lysogenic and lytic cycle?

Answer 12

Temperate phage

Question 13

Why haven’t phages exterminated all bacterium

Answer 13

1. Natural selection
2. Restriction enzymes
3. Lysogenic cycle

Question 14

What do restriction enzymes do?

Answer 14

Identify foreign DNA and cut it up

Question 15

What joins the prophage and host cell’s genome together?

Answer 15

Viral proteins

Question 16

Prophage?

Answer 16

Phage DNA segment in bacteria DNA

Question 17

What triggers lytic mode from lysogenic mode?

Answer 17

Environmental signals (chemical, radiation)

Question 18

How is transcription of prophage genes prevented

Answer 18

Protein coded by prophage prevents its transcription

Question 19

What do nearly all animal viruses have?

Answer 19

Membrane and RNA

Question 20

What are glycoproteins made by?

Answer 20

Ribosomes bound to ER

Question 21

What are the 2 ways of creating a viral envelope?

Answer 21

1. Exocytosis; glycoproteins use host cell membrane

2. Host envelope replaced by Golgi apparatus membrane

Question 22

What are the three types of RNA genomes found in animal viruses?

Answer 22

1. Directly as mRNA
2. Template for mRNA to be transcribed from
3. Retroviruses

Question 23

In retroviruses, what transcribes the RNA to DNA?

Answer 23

Reverse transcriptase

Question 24

HIV contains what?

Answer 24

2 RNA molecules and 2 reverse transcriptase

Question 25

Provirus

Answer 25

DNA (transcribed from RNA) incorporated into host’s genome

Question 26

What can the RNA transcribed from a proviral DNA strand do?

Answer 26

1. Serve as mRNA for viral protein synthesis

2. Serve as genome for new viruses

Question 27

What are the 2 DNA molecules viruses are like

Answer 27

Plasmids and transposons

Question 28

What do plasmids do?

Answer 28

They work apart from cell’s genome and can tranfer between cells

Question 29

What do transposons do?

Answer 29

DNA segments that can move within cell’s genome

Question 30

Difference between provirus and prophage?

Answer 30

Provirus stays permanently in host’s genome, prophage can turn lytic