Micro chapter 8

T/F: Most enveloped viruses exit the host cell through cell lysis.

False

T/F: The main function of a host cell receptor is to specifically bind to the viral attachment protein.

False

T/F: Reverse transcriptase is an RNA-dependent DNA polymerase.

True

AZT is a nucleotide analog used to treat people infected with a) herpes virus. b) HIV. c) papilloma virus. d) influenza virus. e) polio virus.

b) HIV.

Most enveloped viruses exit the cell by the following process a) exocytosis. b) budding. c) Golgi transport. d) cell lysis. e) cytokinesis.

b) budding.

The viral attachment protein specifically binds to a host cell receptor. All of the following are examples of known host cell receptors except a) DNA. b) proteins. c) glycoproteins. d) lipopolysaccharides. e) sialic acids

a) DNA.

A chemical that is structurally similar to a normal nucleoside is called a nucleoside _______.

analog

Antibodies produced in response to a viral infection may specifically bind to the virus particle to effectively block _______________ to the host cell.

attachment

Plant viruses often gain entry into host cells by a) receptor mediated endocytosis. b) injury caused by insects to host cell. c) membrane fusion mechanism. d) pinocytosis. e) direct injection of nucleic acid into the host cell.

b) injury caused by insects to host cell.

Antiviral drugs that act at the level of host recognition are designed to a) prevent endocytotic vesicle formation. b) prevent virus binding to the host cell receptor. c) enhance antibody production. d) inactivate viral nucleic acid polymerases. e) bind to viral metabolic enzymes.

b) prevent virus binding to the host cell receptor.

The ability of a virus or bacteriophage to specifically attach to a host cell occurs through the interactions of the viral attachment protein with the host cell receptor. This binding determines a) the rate of viral replication. b) the host range. c) the mechanism of viral entry. d) whether or not the virus will contain an envelope. e) the rate of viral RNA replication

b) the host range.

The enzyme _______ has a high affinity for AZT and will incorporate it into a newly synthesized DNA strand. This will effectively terminate DNA replication because the incoming nucleotide cannot be bound to AZT. a) host cell DNA polymerase b) viral reverse transcriptase c) host cell RNA polymerase d) viral RNA polymerase e) viral DNA-dependent DNA polymerase

b) viral reverse transcriptase

Most enveloped viruses exit their host cell through a process called __________.

budding

Phage lambda (λ) is referred to as a temperate phage. What is a temperate phage? a) A phage that always causes a lytic infection. b) The same thing as a lysogen. c) A phage that only lyses a cell at a specific temperature. d) A phage that can undergo either a lytic or lysogenic phase of replication. e) A bacteriophage that contains single-stranded RNA for its genome.

d) A phage that can undergo either a lytic or lysogenic phase of replication.

Protease inhibitors are routinely used in the treatment of an HIV infection to slow down the progression of the disease. How do these inhibitors work? a) They inhibit the process of translation for the production of viral proteins. b) They inhibit the process of entry by interacting with the fusion peptide. c) They block the attachment process by interacting with the viral attachment protein. d) They inhibit the proteolytic modification of the viral capsid to form an infectious virion. e) They inhibit the activity of the viral enzyme reverse transcriptase.

d) They inhibit the proteolytic modification of the viral capsid to form an infectious virion.

A viral fusion peptide contains a short hydrophobic amino acid sequence that helps facilitate membrane fusion of the viral envelope to the cell membrane for entry into the host cell. The protein _____________ functions as a fusion peptide for HIV entry into the host cell.

gp41

A bacterial cell that contains the integrated genome of a temperate bacteriophage is called a ______.

lysogen

_________ __________ _________ is initiated by the binding of a virus to a host cell receptor for the entry of the virus into the host cell via an endosome.

Receptor-mediated endocytosis

A bacteriophage genome that is integrated into the bacterial chromosome is called a) a prophage. b) a virulent phage. c) a transforming phage. d) a genome phage.

a) a prophage.

Class III viruses, double-stranded RNA viruses, utilize the following polymerase for genome synthesis a) host cell RNA-dependent RNA polymerase. b) host cell DNA-dependent RNA polymerase. c) viral RNA-dependent RNA polymerase. d) viral DNA-dependent RNA polymerase. e) viral DNA-dependent DNA polymerase.

c) viral RNA-dependent RNA polymerase.

Many antiviral drugs are nucleoside analogs. The nucleoside analogs primarily target these enzymes a) host cell DNA polymerases. b) host cell RNA polymerases. c) host cell nucleases. d) viral nucleic acid polymerases. e) viral nucleases.

d) viral nucleic acid polymerases.

T/F: A nucleoside analog is a short nucleotide sequence that is complementary to a viral promoter sequence.

False

T/F: The second step in viral replication, "entry", is prevented by some antiviral drugs.

True

T/F: The single-stranded RNA of positive-sense RNA viruses can act directly as mRNA for translation in the cytoplasm of the host cell.

True

T/F: Translation of mRNA for the production of viral proteins always takes place in the cytoplasm of eukaryotic cells.

True

The influenza virus gains entry into a host cell by an endocytotic process. The viral nucleocapsid leaves the endosome and enters the cytoplasm through a membrane fusion mechanism. Fusion of the viral envelope with the endosomal membrane is facilitated by a) a conformation change in the hemagglutinin to expose a fusion protein. b) the production of a lipase by the influenza virus. c) sialic acid residues of the receptor proteins. d) specific viral protein recognition of pores in the endosome vesicle. e) the production of proteases by the influenza virus.

a) a conformation change in the hemagglutinin to expose a fusion protein.

Most RNA viruses utilize a) an RNA-dependent RNA polymerase. b) a DNA-dependent RNA polymerase. c) an RNA-dependent DNA polymerase. d) a DNA-dependent DNA polymerase. e) reverse transcriptase.

a) an RNA-dependent RNA polymerase.

Class I viruses, double-stranded DNA viruses, usually utilize the following polymerases for mRNA synthesis and DNA replication a) host cell DNA-dependent RNA polymerase and host cell DNA-dependent DNA polymerase. b) viral DNA-dependent RNA polymerase and viral DNA-dependent DNA polymerase. c) viral RNA-dependent RNA polymerase and host cell DNA-dependent DNA polymerase. d) host cell RNA-dependent RNA polymerase and host cell DNA-dependent DNA polymerase. e) viral RNA-dependent RNA polymerase and viral DNA-dependent DNA polymerase.

a) host cell DNA-dependent RNA polymerase and host cell DNA-dependent DNA polymerase.

Bacteriophage T4 lyses the bacterial host cell for release of newly formed virions. The cell wall of the bacterium is broken down by this virally encoded enzyme a) lysozyme. b) protease. c) β-lactamase. d) nuclease. e) peptidase.

a) lysozyme.

The Baltimore classification scheme classifies viruses based on their mechanism of mRNA synthesis. Using this classification scheme, all viruses are placed into ______ classes. a) seven b) five c) four d) ten e) twenty five

a) seven

E. coli strain K12 is susceptible to infection by phage T2. T2 binds to K12 via two attachment proteins. These two proteins specifically bind to the following two host cell receptor proteins found on the surface of strain K12. a) lipopolysaccharide and cytochrome c b) flagellin and cytochrome c c) OmpF and lipopolysaccharide d) OmpF and flagellin e) flagellin and lipopolysaccharide

c) OmpF and lipopolysaccharide

Which of the following viral replication processes would not be a good target for an antiviral drug? a) Attachment b) Viral entry c) Translation of viral proteins d) Uncoating of viral capsid e) Assembly of virus capsid

c) Translation of viral proteins

The second step in viral replication is entry. For bacteriophage, entry usually involves a) phagocytosis. b) receptor-mediated endocytosis. c) direct entry of the nucleic acid into the cell. d) membrane fusion mechanism of entry. e) digestion of the peptidoglycan.

c) direct entry of the nucleic acid into the cell.

The Baltimore classification scheme for viruses divides all viruses into seven groups based on a) their shape and host. b) host and presence or absence of an envelope. c) how they produce mRNA and replicate their genome. d) their shape and presence or absence of an envelope. e) their shape, host, and presence or absence of an envelope.

c) how they produce mRNA and replicate their genome.

HIV enters the cell through a/an _________ mechanism. a) phagocytic b) receptor-mediated endocytotic c) membrane fusion d) acid-dependent endosomal e) receptor-independent endocytotic

c) membrane fusion

An HIV mutant has been identified that is resistant to the drug AZT. Most likely the mutation occurred in the viral gene that encodes for a) the DNA integrase. b) the viral attachment protein. c) reverse transcriptase. d) gp41 membrane fusion protein. e) viral mRNA polymerase.

c) reverse transcriptase.

The intact virion of the tobacco mosaic virus is assembled by this method a) the capsid is first assembled and the nucleic acid is packaged into the capsid. b) part of the capsid is assembled and the nucleic acid is packaged into the capsid. c) the capsid proteins assemble around the viral nucleic acid. d) the nucleic acid is inserted into the cell membrane and the capsid acquires the nucleic acid as it buds through the membrane, e) the capsid is assembled in the cytoplasm and the nucleic acid is packaged in the nucleus.

c) the capsid proteins assemble around the viral nucleic acid.

The reason nucleoside analogs are effective against viral nucleic acid polymerases is because a) viral polymerases have a very high rates of polymerization. b) viral polymerases have a low rate of polymerization. c) viral polymerases have a high affinity for incorporation of the analogs. d) viral polymerase activity is inhibited by the analogs. e) viral polymerase activity is enhanced by the analogs

c) viral polymerases have a high affinity for incorporation of the analogs.

Antibody produced in response to a viral infection is able to neutralize viral attachment by a) binding nucleic acid polymerases and preventing viral nucleic acid replication. b) binding ribosomes and preventing viral protein translation. c) activating macrophages to phagocytize the virus. d) binding to the viral attachment proteins to prevent attachment to the host cell receptor. e) binding to the host cell receptor molecule to prevent the attachment of the virus.

d) binding to the viral attachment proteins to prevent attachment to the host cell receptor.

Most non-enveloped viruses exit the cell by the following process a) exocytosis. b) budding. c) Golgi transport. d) cell lysis. e) cytokinesis.

d) cell lysis.

Most likely, "host specificity" of a virus is determined by a) the type of nucleic acid it contains. b) the presence or absence of an envelope. c) viral enzymes. d) interactions between viral attachment proteins and host cell receptors. e) viral nucleic acid replication strategies.

d) interactions between viral attachment proteins and host cell receptors.

For most double-stranded DNA eukaryal viruses, DNA replication occurs in the _________ and translation occurs in the __________. a) cytoplasm, cytoplasm b) cytoplasm, nucleus c) nucleus, nucleus d) nucleus, cytoplasm e) mitochondria, cytoplasm

d) nucleus, cytoplasm

The influenza virus gains entry into a host cell by a) direct injection of its nucleic acid. b) receptor-independent endocytosis. c) lysis of the cell membrane. d) receptor-mediated endocytosis. e) pinocytosis.

d) receptor-mediated endocytosis.

Most non-enveloped viruses enter the host cell by receptor-mediated endocytosis. The virus or its nucleic acid is able to leave the endosome and enter the cytoplasm a) through the production of a lipase to lyse the endosome membrane. b) as a result of digestive enzymes found in the endosome. c) through the fusion of the capsid proteins with endosome proteins by digesting the endosomal membrane. d) through pores formed from viral capsid proteins.

d) through pores formed from viral capsid proteins.

Fuzeon is an antiviral drug that prevents membrane fusion for entry into the cell by HIV. The mode of action for this drug is a) to prevent formation of a viral lipase that lyses the cell membrane. b) to prevent attachment of the virus to the host cell receptor. c) to interrupt receptor mediated endocytosis. d) to bind to gp41 membrane fusion protein of HIV. e) to digest the envelope of HIV, thereby preventing membrane fusion.

d) to bind to gp41 membrane fusion protein of HIV.

Class V viruses, negative sense single-stranded RNA viruses, utilize the following polymerase for mRNA synthesis a) viral DNA-dependent RNA polymerase. b) host cell RNA-dependent RNA polymerase. c) host cell DNA-dependent RNA polymerase. d) viral RNA-dependent RNA polymerase. e) don't need polymerase, nucleic acid can act directly as mRNA.

d) viral RNA-dependent RNA polymerase.

Class VII viruses, double-stranded DNA viruses that utilize reverse transcriptase, replicate their genome using the following polymerase a) host cell DNA-dependent DNA polymerase. b) viral DNA-dependent DNA polymerase. c) viral DNA-dependent RNA polymerase. d) viral RNA-dependent DNA polymerase. e) host cell DNA-dependent RNA polymerase.

e) host cell DNA-dependent RNA polymerase.

Most non-enveloped animal viruses enter the host cell by a) membrane fusion. b) pinocytosis. c) injection of nucleic acid into host cell. d) lysis of host cell membrane. e) receptor mediated endocytosis.

e) receptor mediated endocytosis.

Host __________ is determined through the specific binding of the viral attachment protein to the host cell receptor.

range or specificity