CHAP 13

Question 1

What are acellular disease-causing agents that lack cell structure and cannot metabolize, grow, self- reproduce, or respond to their environment.

Answer 1

Viruses, viroids, and prions

Question 2

a tiny infectious agent with nucleic acid

Answer 2

Virus

Question 3

nucleic acid surrounded by proteinaceous capsomeres that form a coat are called?

Answer 3

Capsid

Question 4

It exists in an extracellular state and an intracellular state

Answer 4

Virus

Question 5

a complete viral particle, including a nucleic acid and a capsid, outside a cell.

Answer 5

Virion

Question 6

They include either DNA or RNA. Viral genomes may be dsDNA, ssDNA, dsRNA, or ssRNA They may exist as linear or circular and singular or multiple molecules of nucleic acid, depending on the type.

Answer 6

Genomes of virus

Question 7

are specific for their hosts’ cells because viral attachment molecules are complementary in shape to specific receptor mole- cules on the host’s cells.

Answer 7

Virus

Question 8

All types of organisms can be infected by ?

Answer 8

Viruses

Question 9

a virus that infects a bacterial cell.

Answer 9

bacteriophage

Question 10

can have a membranous envelope or be naked—that is, have no envelope.

Answer 10

Virions

Question 11

are classified based on type of nucleic acid, presence of an
envelope, shape, and size.

Answer 11

Viruses

Question 12

Who has recognized viral family and genus names. With the exception of three orders, higher taxa are not established.

Answer 12

International Committee on Taxonomy of Viruses (ICTV)

Question 13

Viruses depend on random contact with a specific host cell type for replication. Typically, a virus in a cell proceeds with what cycle?

Answer 13

lytic replication cycle

Question 14

What are the stages of lytic replication cycle?

Answer 14

attachment, entry, synthesis, assembly, and release.

Question 15

With animal viruses, the entire virion often enters the cell, where the capsid is then removed in a process called

Answer 15

Uncoating

Question 16

Within the host cell, the viral nucleic acid directs synthesis of more viruses using what?

Answer 16

metabolic enzymes and ribosomes of the host cell.

Question 17

Assembly of synthesized virions occurs in?

Answer 17

Host cell

Question 18

Virions are released from the host cell either by?

Answer 18

lysis of the host cell (seen with phages and animal viruses) or by the extrusion of enveloped virions through the host’s cytoplasmic membrane (budding)

Question 19

a process seen only with certain animal viruses.

Answer 19

Budding

Question 20

Temperate phages (lysogenic phages) enter a bacterial cell
and remain inactive in a process called

Answer 20

lysogeny or lysogenic replication cycle

Question 21

inactive phages are called what and are inserted into the chromosome of the cell and passed to its daughter cells.

Answer 21

prophages

Question 22

results when phages carry genes that alter the phenotype of a bacterium

Answer 22

Lysogenic conversion

Question 23

At some point in the generations that follow, a prophage may be excised from the chromosome in a process known as

Answer 23

induction

Question 24

During induction,
the prophage again becomes a

Answer 24

lytic virus

Question 25

**dsDNA** viruses use their DNA like cellular DNA in transcription and replication except?

Answer 25

hepatitis B virus

Question 26

These viruses have positive-sense single-stranded RNA, which can be directly translated by ribosomes to synthesize protein.

Answer 26

ssRNA

Question 27

From the positive-sense single-stranded RNA (∙ssRNA) what is transcribed to serve as a template for more + ssRNA.

Answer 27

complementary negative-sense single-stranded RNA ( - ssRNA)

Question 28

carry reverse transcriptase, which transcribes DNA from RNA.

Answer 28

Retroviruses (HIV, +ssRNA)

Question 29

carry an RNA-dependent RNA transcriptase for transcribing mRNA from the - ssRNA genome, and the mRNA is translated to protein.

Answer 29

Negative-sense single-stranded RNA (-ssRNA)

Question 30

these viruses, the positive strand of RNA functions as mRNA, and each strand functions as a template for an RNA complement.

Answer 30

dsRNA

Question 31

a process similar to lysogeny, an animal virus remains inactive in a cell, possibly for years, as part of a chro- mosome or in the cytosol.

Answer 31

Latency

Question 32

also known as a **provirus**.

Answer 32

Latent virus

Question 33

is uncontrolled cellular reproduction in a multicel- lular animal.

Answer 33

Neoplasia

Question 34

A mass of neoplastic cells

Answer 34

Tumor

Question 35

A mass of neoplastic cells relatively harmless

Answer 35

Benign tumor

Question 36

A mass of neoplastic cells invasive

Answer 36

malignant tumor

Question 37

**Malignant tumors** are also called?

Answer 37

Cancer

Question 38

describes the spreading of malignant tumors.

Answer 38

Metastasis

Question 39

Environmental factors or oncogenic viruses may cause?

Answer 39

Neoplasia

Question 40

In the laboratory, viruses must be cultured inside mature organ- isms, in embryonated chicken eggs, or in cell cultures because?

Answer 40

viruses cannot metabolize or replicate alone.

Question 41

When a mixture of bacteria and phages is grown on an agar plate, bacteria infected with phages lyse, producing clear areas called?

Answer 41

Plaques on the bacterial lawn.

Question 42

A technique used to estimate phage numbers.

Answer 42

Plaque assay

Question 43

Viruses can be grown in two types of ?

Answer 43

Cell cultures

Question 44

What culture last about 100 generations,

Answer 44

diploid cell cultures

Question 45

What cell culture is derived from cancer cells, last longer.

Answer 45

continuous cell cultures

Question 46

Outside cells, viruses do not appear to be alive, but within cells, they exhibit lifelike qualities, such as the ability to replicate. True or False

Answer 46

True

Question 47

are small circular pieces of RNA with no capsid that infect and cause disease in plants

Answer 47

Viroids

Question 48

pathogenic RNA mole- cules have been found in

Answer 48

Fungi

Question 49

are infectious protein particles that lack nucleic acids

Answer 49

Prions

Question 50

replicate by inducing similar, normal proteins to misfold into new prions—a process called

Answer 50

Templating

Question 51

Diseases caused by these are spongiform encephalopathies, which involve fatal neurological degeneration.

Answer 51

Prions

Question 52

Which of the following is not an **acellular agent**? a. viroid c. rickettsia b. virus d. prion

Answer 52

c. rickettsia

Question 53

Which of the following statements is true? a. Viruses move toward their host cells. b. Viruses are capable of metabolism. c. Viruses lack a cytoplasmic membrane. d. Viruses grow in response to their environmental conditions.

Answer 53

c. Viruses **lack** a **cytoplasmic membrane**.

Question 54

A virus that is **specific for a bacterial host** is called a a. phage c. virion b. prion d. viroid

Answer 54

a. phage

Question 55

A naked virus __________________. a. has no membranous envelope b. has injected its DNA or RNA into a host cell c. is devoid of capsomeres d. is one that is unattached to a host cell

Answer 55

a. has **no membranous envelope**

Question 56

Which of the following statements is false? a. Viruses may have circular DNA. b. dsRNA is found in bacteria more often than in viruses. c. Viral DNA may be linear. d. Typically, viruses have DNA or RNA but not both.

Answer 56

b. dsRNA is found in bacteria more often than in viruses.

Question 57

When a eukaryotic cell is infected with an enveloped virus and sheds viruses slowly over time, this infection __________________. a. is called a lytic infection b. is a prophage cycle c. is called a persistent infection d. is caused by a quiescent virus

Answer 57

c. is called a persistent infection

Question 58

Another name for a **complete virus** is __________________. a. virion b. viroid c. prion d. capsid

Answer 58

a. virion

Question 59

Which of the following viruses can be **latent**? a. HIV b. chicken pox virus c. herpesviruses d. all of the above

Answer 59

d. all of the above

Question 60

Which of the following is **not a criterion** for specific family classi- fication of viruses? a. the type of nucleic acid b. envelope structure c. capsid type present d. lipid composition

Answer 60

d. lipid composition

Question 61

10. A **clear zone of phage infection** in a bacterial lawn is __________________. a. a prophage b. a plaque c. naked d. a zone of inhibition

Answer 61

b. a plaque

Question 62

harmless neoplastic cells

Answer 62

benign tumor

Question 63

**invasive** neoplastic cells

Answer 63

cancer

Question 64

**removal of capsomeres** from a virion

Answer 64

uncoating

Question 65

**inactive virus** within bacterial cell.

Answer 65

prophage

Question 66

**complete viral** particle

Answer 66

virion

Question 67

a **membrane on the outside** of a virus.

Answer 67

envelope

Question 68

**protein coat** of virus

Answer 68

Capsid

Question 69

transcribes DNA from RNA

Answer 69

Retrovirus

Question 70

a virus that **infects a bacterium**.

Answer 70

Bacteriophage

Question 71

**dormant virus** in a eukaryotic cell.

Answer 71

Provirus