Ch 17

Question 1

What is a capsid?

Answer 1

protein coat that encloses a viral genome.

Question 2

Define capsomeres

Answer 2

Protein subunits that compose viral capsids.

Question 3

What is a viral envelope?

Answer 3

membrane derived from host cells that surrounds some viral capsids.

Question 4

What is the host range of a virus?

Answer 4

The limited number of species a virus can infect.

Question 5

What is a prophage?

Answer 5

Viral DNA integrated into a host bacterial genome during lysogeny.

Question 6

What is reverse transcriptase?

Answer 6

An enzyme that transcribes RNA into DNA in retroviruses.

Question 7

What is a provirus?

Answer 7

Viral DNA integrated into a host cell’s genome in retroviruses.

Question 8

What are bacteriophages?

Answer 8

Viruses that infect bacteria.

Question 9

What is the lytic cycle?

Answer 9

viral replication cycle that results in the death of the host cell.

Question 10

What is the lysogenic cycle?

Answer 10

viral replication cycle where the virus coexists with its host.

Question 11

T/F: All viruses have double-stranded DNA genomes.

Answer 11

False. Viruses can have single-stranded or double-stranded DNA or RNA genomes.

Question 12

T/F: Viruses can replicate outside of host cells.

Answer 12

False. Viruses are obligate intracellular parasites and can only replicate within host cells.

Question 13

T/F: The viral envelope is made of proteins produced by the virus.

Answer 13

False. The viral envelope is derived from host cell membranes

Question 14

T/F: Bacteriophages infect animal cells.

Answer 14

False. Bacteriophages specifically infect bacteria.

Question 15

T/F: HIV is a retrovirus.

Answer 15

T

Question 16

T/F: All viruses use the lytic cycle for replication.

Answer 16

False. Some viruses use the lysogenic cycle or can alternate between lytic and lysogenic cycles.

Question 17

T/F: Viral genomes always consist of a single molecule.

Answer 17

False. While viral genomes are usually a single molecule, they may consist of multiple molecules.

Question 18

T/F: The lysogenic cycle always results in immediate host cell death.

Answer 18

False. The lysogenic cycle allows for coexistence of the virus and host.

Question 19

T/F: Enveloped viruses enter host cells through fusion with the cell membrane.

Answer 19

T

Question 20

T/F: HIV directly kills T cells upon infection.

Answer 20

False. HIV integrates into the host genome and may not immediately kill the cell.

Question 21

Viruses consist of a nucleic acid genome enclosed in a protein coat called a ________.

Answer 21

capsid

Question 22

The first step of viral replication involves the virus ________ to the host cell.

Answer 22

attaching

Question 23

Viruses that can switch between lytic and lysogenic cycles are called ________ phages.

Answer 23

temperate

Question 24

In HIV, the enzyme ________ ________ transcribes the RNA genome into double-stranded DNA.

Answer 24

reverse transcriptase

Question 25

The ________ cycle of bacteriophages results in the death of the host cell

Answer 25

lytic

Question 26

Viral proteins that bind to receptor molecules on host cells are located on the ________ or envelope.

Answer 26

capsid

Question 27

A virus integrated into the host genome during lysogeny is called a ________.

Answer 27

prophage

Question 28

HIV is classified as a ________ because it transcribes its RNA into DNA before integration.

Answer 28

retrovirus

Question 29

The protein subunits that make up viral capsids are called ________.

Answer 29

capsomeres

Question 30

Viruses can only infect a limited number of species, which is known as their ________ ________.

Answer 30

host range

Question 31

Which of the following is NOT a possible viral genome type?
a) Single-stranded DNA
b) Double-stranded RNA
c) Triple-stranded DNA
d) Single-stranded RNA

Answer 31

c) Triple-stranded DNA

Question 32

How many phage particles are typically released at the end of a lytic cycle?
a) 10-20
b) 50-100
c) 100-200
d) 500-1000

Answer 32

c) 100-200

Question 33

What is the approximate time for a complete lytic cycle at 37°C?
a) 5-10 minutes
b) 20-30 minutes
c) 1-2 hours
d) 4-6 hours

Answer 33

b) 20-30 minutes

Question 34

Which of the following is NOT a step in the basic viral replication cycle?
a) Attachment
b) Entry
c) Photosynthesis
d) Assembly

Answer 34

c) Photosynthesis

Question 35

What percentage of human cancers are related to viral infections?
a) Less than 5%
b) Above 15%
c) Exactly 10%
d) 50-60%

Answer 35

b) Above 15%

Question 36

Which of the following is a characteristic of retroviruses?
a) They have a DNA genome
b) They directly kill host cells upon entry
c) They integrate their genetic material into the host genome
d) They cannot infect human cells

Answer 36

c) They integrate their genetic material into the host genome

Question 37

What type of virus is HIV?
a) DNA virus
b) Bacteriophage
c) Retrovirus
d) Plant virus

Answer 37

c) Retrovirus

Question 38

Which environmental factor can induce a prophage to enter the lytic cycle?
a) Low temperature
b) High-energy radiation (UV)
c) Increased nutrients
d) Decreased oxygen levels

Answer 38

b) High-energy radiation (UV)

Question 39

How many copies of its RNA genome does HIV package into each virion?
a) One
b) Two
c) Three
d) Four

Answer 39

b) Two

Question 40

What is the primary target cell type for HIV infection?
a) Red blood cells
b) Liver cells
c) T cells
d) Skin cells

Answer 40

c) T cells