chapter 25 section 2

Question 1

what is an obligate intracellular parasite?

Answer 1

viruses that depend on host cells for replication

Question 2

what are bacteriophages?

Answer 2

are viruses that infect bacteria

Question 3

short description of the lytic cycle

Answer 3

virus invades host cell, produces new viruses, destroys the host cell, and releases newly formed viruses.

Question 4

short description of the lysogenic cycle

Answer 4

virus infects a cell without causing its immediate destruction; just replication

Question 5

the tail of a bacteriophage is specialized for

Answer 5

injecting the vial nucleic acid into a host cell

Question 6

many viruses infect only a certain type of cell because they recognize

Answer 6

receptor sites on the cell’s surface

Question 7

during the lytic cycle

Answer 7

one of the enzymes coded for by the viral genome causes the host cell to disintegrate

Question 8

during the lysogenic cycle

Answer 8

a prophage or provirus replicates whenever the host cell reproduces

Question 9

some viruses that invade the human body avoid destruction by the immune system by

Answer 9

mutating quickly

Question 10

what kinds of factors can cause a prophage to become virulent

Answer 10

radiation and certain chemicals

Question 11

how does an RNA virus get viral DNA into a host cell’s genome

Answer 11

it releases its RNA into the host cell, and that RNA is transcribed into DNA by reverse transcriptase; the DNA is then integrated into the host cell’s genome

Question 12

why must a person receive a different flu vaccine each year to be protected against the flu?

Answer 12

the influenza virus mutates quickly, producing new strains. the flu vaccine targets a different strain each year.

Question 13

how does the structure and function of bacteriophages make these viruses useful tools for genetic engineering

Answer 13

bacteriophages are very effective at injecting foreign DNA into bacteria. Genetic engineers can use bacteriophages to introduce DNA of interest to humans into bacteria

Question 14

describe the first step of the lytic cycle

Answer 14

virus attaches to the host cell’s surface

Question 15

describe the second step of the lytic cycle

Answer 15

the viral DNA is injected into the host cell

Question 16

describe the third step of the lytic cycle

Answer 16

the viral DNA replicates and directs the synthesis of viral proteins

Question 17

describe the fourth step of the lytic cycle

Answer 17

new virus particles are assembled

Question 18

describe the fifth step of the lytic cycle

Answer 18

the host cell ruptures, releasing the new virus particles

Question 19

viruses that undergo the lytic cycle are called ________ because they cause disease

Answer 19

virulent

Question 20

a virus that does not kill the host cell immediately and replicates through the lysogenic cycle is called a

Answer 20

temperate

Question 21

cell disintegration is called

Answer 21

lysis