Basic Virology Access Medicine

Some viruses are known for their ability to cause perinatal infections. Which one of the following viruses is most likely to cause perinatal infections? A Cytomegalovirus B Epstein-Barr virus C JC virus D Norovirus E Poliovirus

A Cytomegalovirus

Each of the following viruses possesses a DNA polymerase in the virion EXCEPT: A Human immunodeficiency virus B Human T-cell lymphotropic virus C Epstein-Barr virus D Hepatitis B virus

C Epstein-Barr virus

Main site of action of acyclovir A Attachment and penetration of virion B Viral mRNA synthesis C Viral protein synthesis D Viral genome DNA synthesis E Assembly and release of progeny virus

D Viral genome DNA synthesis

Step at which budding occurs A Attachment and penetration of virion B Viral mRNA synthesis C Viral protein synthesis D Viral genome DNA synthesis E Assembly and release of progeny virus

E Assembly and release of progeny virus

Which one of the following best describes the action of oseltamivir (Tamiflu)? A Inhibits reverse transcriptase B Inhibits the RNA-dependent RNA polymerase in the virion C Inhibits the DNA-dependent RNA polymerase in the infected cell D Inhibits viral protein synthesis by binding to the 60S ribosomal subunit E Inhibits the neuraminidase required for release of virus from the infected cell

E Inhibits the neuraminidase required for release of virus from the infected cell

Which one of the following viruses that causes human disease has an animal reservoir? A Cytomegalovirus B Hepatitis C virus C Smallpox virus D Varicella-zoster virus E Yellow fever virus

E Yellow fever virus

Each of the following statements concerning lysogeny is correct EXCEPT: A Viral genes replicate independently of bacterial genes. B Viral genes responsible for lysis are repressed. C Viral DNA is integrated into bacterial DNA. D Some lysogenic bacteriophages encode toxins that cause human disease.

A Viral genes replicate independently of bacterial genes.

The major barrier to the control of rhinovirus upper respiratory infections by immunization is: A The poor local and systemic immune response to these viruses B The large number of serotypes of the rhinoviruses C The side effects of the vaccine D The inability to grow the viruses in cell culture

B The large number of serotypes of the rhinoviruses

A stock of virus particles has been found by electron microscopy to contain 10^8 particles/mL, but a plaque assay reveals only 10^5 plaque-forming units/mL. The BEST interpretation of these results is that: A Only one particle in 1000 is infectious. B A nonpermissive cell line was used for the plaque assay. C Several kinds of viruses were present in the stock. D The virus is a temperature-sensitive mutant.

A Only one particle in 1000 is infectious.

Which one of the following forms of immunity to viruses would be LEAST likely to be lifelong? A Passive immunity B Passive-active immunity C Active immunity D Cell-mediated immunity

A Passive immunity

Function of virion polymerase of influenza virus A Attachment and penetration of virion B Viral mRNA synthesis C Viral protein synthesis D Viral genome DNA synthesis E Assembly and release of progeny virus

B Viral mRNA synthesis

Each of the following statements concerning viral surface proteins is correct EXCEPT: A They elicit antibody that neutralizes infectivity of the virus. B They determine the species specificity of the virus-cell interaction. C They participate in active transport of nutrients across the viral envelope membrane. D They protect the genetic material against nucleases.

C They participate in active transport of nutrients across the viral envelope membrane.

You have isolated a virus from the stool of a patient with diarrhea and shown that its genome is composed of multiple pieces of double-stranded RNA. Which one of the following is LEAST LIKELY to be true? A Each piece of RNA encodes a different protein. B The virus encodes an RNA-directed RNA polymerase. C The virion contains an RNA polymerase. D The genome integrates into the host chromosome.

D The genome integrates into the host chromosome.

Regarding the tegument, which one of the following is most accurate? A It uncoats the virion within the phagocytic vesicle. B It mediates the binding of the virion to the cell surface. C It guides the viral core from the cytoplasm to the nucleus. D It is the site at which new virions bud from the surface of the infected cell. E It is the location of proteins in the virion that act as viral transcription factors.

E It is the location of proteins in the virion that act as viral transcription factors.

An envelope protein induces the formation of giant cells. A Poliovirus B Epstein-Barr virus C Prions D Hepatitis B virus E Respiratory syncytial virus

E Respiratory syncytial virus

Main site of action of amantadine A Attachment and penetration of virion B Viral mRNA synthesis C Viral protein synthesis D Viral genome DNA synthesis E Assembly and release of progeny virus

A Attachment and penetration of virion

Main site of action of antiviral antibody A Attachment and penetration of virion B Viral mRNA synthesis C Viral protein synthesis D Viral genome DNA synthesis E Assembly and release of progeny virus

A Attachment and penetration of virion

Each of the following viruses possesses double-stranded nucleic acid as its genome EXCEPT: A Coxsackie virus B Herpes simplex virus C Rotavirus D Adenovirus

A Coxsackie virus

Herpes simplex virus A DNA enveloped virus B DNA nonenveloped virus C RNA enveloped virus D RNA nonenveloped virus

A DNA enveloped virus

Each of the following viruses possesses an RNA polymerase in the virion EXCEPT: A Hepatitis A virus B Smallpox virus C Mumps virus D Rotavirus

A Hepatitis A virus

Nonenveloped RNA virus that is transmitted by the fecal-oral route A Hepatitis A virus B Hepatitis B virus C Hepatitis C virus D Hepatitis D virus

A Hepatitis A virus

You have isolated two mutants of poliovirus, one mutated at gene X and the other mutated at gene Y. If you infect cells with each one alone, no virus is produced. If you infect a single cell with both mutants, which one of the following statements is most accurate? A If complementation between the mutant gene products occurs, both X and Y progeny viruses will be made. B If phenotypic mixing occurs, then both X and Y progeny viruses will be made. C If the genome is transcribed into DNA, then both X and Y viruses will be made. D Because reassortment of the genome segments occurs at high frequency, both X and Y progeny viruses will be made.

A If complementation between the mutant gene products occurs, both X and Y progeny viruses will be made.

Each of the following statements concerning the viruses that infect humans is correct EXCEPT: A Only viruses with a negative polarity RNA genome have a polymerase in the virion. B The purified nucleic acid of some viruses is infectious, but at a lower efficiency than the intact virions. C Some viruses contain lipoprotein envelopes derived from the plasma membrane of the host cell. D The nucleic acid of some viruses is single-stranded DNA and that of others is double-stranded RNA.

A Only viruses with a negative polarity RNA genome have a polymerase in the virion.

The translation product of viral mRNA is a polyprotein that is cleaved to form virion structural proteins. A Poliovirus B Epstein-Barr virus C Prions D Hepatitis B virus E Respiratory syncytial virus

A Poliovirus

The purified genome of certain viruses can enter a cell and elicit the production of progeny viruses (i.e., the genome is infectious). Regarding these viruses, which one of the following statements is most accurate? A Their genome RNA has positive polarity. B Their genome RNA is double-stranded. C They have a polymerase in the virion. D They have a segmented genome. E They require tegument proteins in order to be infectious.

A Their genome RNA has positive polarity.

The proteins on the external surface of viruses serve several important functions. Regarding these proteins, which one of the following statements is most accurate? A They are the antigens against which neutralizing antibodies are formed. B They are the polymerases that synthesize viral messenger RNA. C They are the proteases that degrade cellular proteins leading to cell death. D They are the proteins that regulate viral transcription. E Change in conformation of these proteins can result in prion-mediated diseases such as Creutzfeldt-Jakob disease.

A They are the antigens against which neutralizing antibodies are formed.

Which one of the following is the BEST explanation for the selective action of acyclovir (acycloguanosine) in herpes simplex virus (HSV)-infected cells? A Acyclovir binds specifically to viral receptors only on the surface of the HSV-infected cell. B Acyclovir is phosphorylated by a virus-encoded phosphokinase only within HSV-infected cells. C Acyclovir selectively inhibits the RNA polymerase in the HSV virion. D Acyclovir specifically blocks the matrix protein of HSV, thereby preventing release of progeny HSV.

B Acyclovir is phosphorylated by a virus-encoded phosphokinase only within HSV-infected cells.

Human papillomavirus A DNA enveloped virus B DNA nonenveloped virus C RNA enveloped virus D RNA nonenveloped virus

B DNA nonenveloped virus

It causes latent infection of B cells. A Poliovirus B Epstein-Barr virus C Prions D Hepatitis B virus E Respiratory syncytial virus

B Epstein-Barr virus

Many viruses use the upper respiratory tract (mouth, nasopharynx) as their important portal of entry. One feature of the portal of entry is that it is the site where the virus first infects and replicates. Which one of the following viruses is most likely to enter via the upper respiratory tract? A Dengue virus B Epstein-Barr virus C Hepatitis A virus D Hepatitis B virus E Rotavirus

B Epstein-Barr virus

Induction of passive-active immunity is useful in the prevention of which one of the following sets of two viral diseases? A Hepatitis A and dengue B Hepatitis B and rabies C Influenza and varicella D Mumps and yellow fever E Rubella and measles

B Hepatitis B and rabies

Enveloped DNA virus that is transmitted by blood A Hepatitis A virus B Hepatitis B virus C Hepatitis C virus D Hepatitis D virus

B Hepatitis B virus

Purified surface protein of this virus is the immunogen in a vaccine A Hepatitis A virus B Hepatitis B virus C Hepatitis C virus D Hepatitis D virus

B Hepatitis B virus

Protection of the unimmunized individual based on immunization of a sufficient number of other members of the population is a description of which one of the following? A Active immunity B Herd immunity C Passive immunity D Passive-active immunity E Postexposure immunity

B Herd immunity

Seeing multinucleated giant cells in a Tzanck smear can be used to make a presumptive diagnosis of infection by which one of the following viruses? A Epstein-Barr virus B Herpes simplex virus C Human papillomavirus D Parvovirus B19 E Rubella virus

B Herpes simplex virus

Latency is an outcome particularly characteristic of which one of the following virus groups? A Polioviruses B Herpesviruses C Rhinoviruses D Influenza viruses

B Herpesviruses

Which one of the following choices names two viruses that both translate their messenger RNA into precursor polypeptides that must be cleaved by virion-encoded proteases? A Herpes simplex virus and human papillomavirus B Human immunodeficiency virus and poliovirus C Influenza virus and measles virus D Rabies virus and hepatitis B virus E Rotavirus and parvovirus

B Human immunodeficiency virus and poliovirus

Viruses can cause changes in individual cells that are visible in the light microscope after suitable staining. Which one of the following is most characteristic of the changes seen in rabies virus-infected cells? A Inclusion bodies in the cytoplasm of macrophages B Inclusion bodies in the cytoplasm of neurons C Inclusion bodies in the nucleus of neurons D Multinucleated giants cells composed of neurons E Multinucleated giants cells composed of macrophages

B Inclusion bodies in the cytoplasm of neurons

Which one of the following statements concerning alpha, beta, and gamma interferons is LEAST accurate? A Interferons inhibit a broad range of viruses, not just the virus that induced the interferon. B Interferons are synthesized only by virus-infected cells. C Interferons induce the synthesis of a protein kinase that phosphorylates an elongation factor, thereby inactivating protein synthesis. D Interferons induce the synthesis of a ribonuclease that degrades viral mRNA.

B Interferons are synthesized only by virus-infected cells.

Each of the following viruses possesses an outer envelope of lipoprotein EXCEPT: A Varicella-zoster virus B Papillomavirus C Influenza virus D Human immunodeficiency virus

B Papillomavirus

In the lab, a virologist was studying the properties of HIV. She infected the same cell with both HIV and rabies virus. (HIV can infect only human CD4-positive cells, whereas rabies virus can infect both human cells and dog cells.) Some of the progeny virions were able to infect dog cells, within which she found HIV-specific RNA. Which one of the following is the term used to describe these results? A Complementation B Phenotypic mixing C Reassortment D Recombination

B Phenotypic mixing

Regarding viral replication, which one of the following is most accurate? A The cytopathic effect typically occurs during the eclipse period. B The early proteins are typically enzymes, whereas the late proteins are typically capsid proteins. C The assembly of a nonenveloped virus typically occurs as the virion buds from the cell membrane. D Influenza viruses synthesize their mRNA using host cell-encoded RNA-dependent RNA polymerase. E Retroviruses (e.g., HIV) synthesize their mRNA using an enzyme in the virion called reverse transcriptase.

B The early proteins are typically enzymes, whereas the late proteins are typically capsid proteins.

Viruses enter cells by adsorbing to specific sites on the outer membrane of cells. Each of the following statements regarding this event is correct EXCEPT: A The interaction determines the specific target organs for infection. B The interaction determines whether the purified genome of a virus is infectious. C The interaction can be prevented by neutralizing antibody. D If the sites are occupied, interference with virus infection occurs.

B The interaction determines whether the purified genome of a virus is infectious.

Each of the following statements concerning retroviruses is correct EXCEPT: A The virion carries an RNA-directed DNA polymerase encoded by the viral genome. B The viral genome consists of three segments of double-stranded RNA. C The virion is enveloped and enters cells via an interaction with specific receptors on the host cell. D During infection, the virus synthesizes a DNA copy of its RNA, and this DNA becomes covalently integrated into host cell DNA.

B The viral genome consists of three segments of double-stranded RNA.

Each of the following statements about both measles virus and rubella virus is correct EXCEPT: A They are RNA enveloped viruses. B Their virions contain an RNA polymerase. C They have a single antigenic type. D They are transmitted by respiratory aerosol.

B Their virions contain an RNA polymerase.

Regarding viroids, which one of the following statements is the MOST accurate? A They are defective viruses that are missing the DNA coding for the matrix protein. B They consist of RNA without a protein or lipoprotein outer coat. C They cause tumors in experimental animals. D They require an RNA polymerase in the particle for replication to occur.

B They consist of RNA without a protein or lipoprotein outer coat.

Reasonable mechanisms for viral persistence in infected individuals include all of the following EXCEPT: A Generation of defective-interfering particles B Virus-mediated inhibition of host DNA synthesis C Integration of a provirus into the genome of the host D Host tolerance to viral antigens

B Virus-mediated inhibition of host DNA synthesis

Individuals who have had an anaphylactic reaction to egg proteins should NOT receive which one of the following vaccines? A Hepatitis A vaccine B Hepatitis B vaccine C Influenza vaccine D Polio vaccine E Rabies vaccine

C Influenza vaccine

Enveloped RNA virus that is the most common cause of non-A, non-B hepatitis A Hepatitis A virus B Hepatitis B virus C Hepatitis C virus D Hepatitis D virus

C Hepatitis C virus

If a virus has an envelope, it is more easily inactivated by lipid solvents and detergents than viruses that do not have an envelope. Which one of the following viruses is the most sensitive to inactivation by lipid solvents and detergents? A Coxsackie virus B Hepatitis A virus C Herpes simplex virus D Poliovirus E Rotavirus

C Herpes simplex virus

Regarding immunologic aspects of viral diseases, which one of the following is most accurate? A Antibodies protect against some viral diseases by inhibiting the synthesis of mRNA by the RNA polymerase in the virion. B IgG plays a major role in neutralizing virus infectivity during the primary infection. C IgA exerts an antiviral effect by preventing virus from infecting the mucosal cells of the respiratory and gastrointestinal tracts. D IgE can prevent viral infection by activating complement, which leads to the production of the membrane attack complex. E Interleukin-2 is important in protecting uninfected cells from viral infection by inhibiting the release of virus from infected cells.

C IgA exerts an antiviral effect by preventing virus from infecting the mucosal cells of the respiratory and gastrointestinal tracts.

Regarding the mode of action of interferon, which one of the following is the most accurate? A It acts by inhibiting the virion protease. B It acts by inhibiting the virion polymerase. C It acts by inducing a ribonuclease that degrades viral mRNA. D It acts by binding to the extracellular virion, thereby preventing entry into the cell. E It acts against viruses with a DNA genome but not against viruses that have RNA as their genome.

C It acts by inducing a ribonuclease that degrades viral mRNA.

A temperate bacteriophage has been induced from a new pathogenic strain of Escherichia coli that produces a toxin. Which one of the following is the MOST convincing way to show that the phage encodes the toxin? A Carry out conjugation of the pathogenic strain with a nonpathogenic strain. B Infect an experimental animal with the phage. C Lysogenize a nonpathogenic strain with the phage. D Look for transposable elements in the phage DNA.

C Lysogenize a nonpathogenic strain with the phage.

It is remarkably resistant to ultraviolet light. A Poliovirus B Epstein-Barr virus C Prions D Hepatitis B virus E Respiratory syncytial virus

C Prions

Biochemical analysis of a virus reveals the genome to be composed of eight unequally sized pieces of single-stranded RNA, each of which is complementary to viral mRNA in infected cells. Which one of the following statements is UNLIKELY to be correct? A Different proteins are encoded by each segment of the viral genome. B The virus particle contains a virus-encoded enzyme that can copy the genome into its complement. C Purified RNA extracted from the virus particle is infectious. D The virus can acquire new antigens via reassortment of its RNA segments.

C Purified RNA extracted from the virus particle is infectious.

Human T-cell lymphotropic virus A DNA enveloped virus B DNA nonenveloped virus C RNA enveloped virus D RNA nonenveloped virus

C RNA enveloped virus

The feature of the influenza virus genome that contributes MOST to the antigenic variation of the virus is: A A high G + C content, which augments binding to nucleo-proteins B Inverted repeat regions, which create "sticky ends" C Segmented nucleic acid D Unique methylated bases

C Segmented nucleic acid

Your summer research project is to study the viruses that cause upper respiratory tract infections. You have isolated a virus from a patient's throat and find that its genome is RNA. Furthermore, you find that the genome is the complement of viral mRNA within the infected cell. Of the following, which is the most appropriate conclusion you could draw? A The genome RNA is infectious. B The genome RNA is segmented. C The virion contains a polymerase. D The virion has a lipoprotein envelope. E A single-stranded DNA is synthesized during replication.

C The virion contains a polymerase.

Each of the following statements about both poliovirus and rhinoviruses is correct EXCEPT: A They are nonenveloped RNA viruses. B They have multiple antigenic types. C Their virions contain an RNA polymerase. D They do not integrate their genome into host cell DNA.

C Their virions contain an RNA polymerase.

Viruses are obligate intracellular parasites. Each of the following statements concerning this fact is correct EXCEPT: A Viruses cannot generate energy outside of cells. B Viruses cannot synthesize proteins outside of cells. C Viruses must degrade host cell DNA in order to obtain nucleotides. D Enveloped viruses require host cell membranes to obtain their envelopes.

C Viruses must degrade host cell DNA in order to obtain nucleotides.

Each of the following statements concerning viral vaccines is correct EXCEPT: A In live, attenuated vaccines, the virus has lost its ability to cause disease but has retained its ability to induce neutralizing antibody. B In live, attenuated vaccines, the possibility of reversion to virulence is of concern. C With inactivated vaccines, IgA mucosal immunity is usually induced. D With inactivated vaccines, protective immunity is due mainly to the production of IgG.

C With inactivated vaccines, IgA mucosal immunity is usually induced.

The term vertical transmission refers to: A transmission by insect vector from reservoir to patient. B transmission from a sex worker to a client. C transmission from mother to child. D transmission from one child to another at school. E transmission from person to person within a family.

C transmission from mother to child.

Which one of the following best describes the mechanism by which immunopathogenesis occurs? A Ability of antibodies to block pathogenesis by viruses B Ability of cytotoxic T cells to block pathogenesis by viruses C Ability of neutrophils to block pathogenesis by viruses D Ability of cytotoxic T cells to cause pathogenesis by viruses E Ability of eosinophils to cause pathogenesis by viruses

D Ability of cytotoxic T cells to cause pathogenesis by viruses

Each of the following statements about human immunodeficiency virus (HIV) is correct EXCEPT: A HIV is an enveloped RNA virus. B The virion contains an RNA-dependent DNA polymerase. C A DNA copy of the HIV genome integrates into host cell DNA. D Acyclovir inhibits HIV replication.

D Acyclovir inhibits HIV replication.

Which one of the following statements about virion structure and assembly is CORRECT? A Most viruses acquire surface glycoproteins by budding through the nuclear membrane. B Helical nucleocapsids are found primarily in DNA viruses. C The symmetry of virus particles prevents inclusion of any nonstructural proteins, such as enzymes. D Enveloped viruses use a matrix protein to mediate interactions between viral glycoproteins in the plasma membrane and structural proteins in the nucleocapsid.

D Enveloped viruses use a matrix protein to mediate interactions between viral glycoproteins in the plasma membrane and structural proteins in the nucleocapsid.

Part of the genome DNA is synthesized by the virion polymerase. A Poliovirus B Epstein-Barr virus C Prions D Hepatitis B virus E Respiratory syncytial virus

D Hepatitis B virus

Enveloped RNA virus that has the surface antigen of another virus A Hepatitis A virus B Hepatitis B virus C Hepatitis C virus D Hepatitis D virus

D Hepatitis D virus

Each of the following statements concerning interferon is correct EXCEPT: A Interferon inhibits the growth of both DNA and RNA viruses. B Interferon is induced by double-stranded RNA. C Interferon made by cells of one species acts more effectively in the cells of that species than in the cells of other species. D Interferon acts by preventing viruses from entering the cell.

D Interferon acts by preventing viruses from entering the cell.

Regarding viral vaccines, which one of the following is the MOST accurate? A Killed vaccines induce a longer lasting response than do live, attenuated vaccines. B Killed vaccines are no longer used in this country because they do not induce secretory IgA. C Killed vaccines induce a broader range of immune responses than do live, attenuated vaccines. D Killed vaccines are safer to give to immunocompromised patients than are live, attenuated vaccines.

D Killed vaccines are safer to give to immunocompromised patients than are live, attenuated vaccines.

Which one of the following is a well-described adverse effect of the protease inhibitors used in the treatment of HIV infection? A Bone marrow suppression B Central nervous system disturbances C Drug-induced hepatitis D Lipodystrophy E Peripheral neuropathy

D Lipodystrophy

Regarding the viral growth cycle, which one of the following is most accurate? A During the lysogenic phase, the typical result is the production of hundreds of progeny virions. B Hepatitis B virus has an RNA polymerase in the virion that is required to synthesize messenger RNA from the positive strand of the viral DNA. C Herpesviruses have an RNA-dependent DNA polymerase in the virion. D Lysogenic conversion is the process by which bacteria acquire new genes due to transduction by a lysogenic bacteriophage. E Smallpox virus translates its genome into a single polypeptide, which is then cleaved into structural and nonstructural proteins.

D Lysogenic conversion is the process by which bacteria acquire new genes due to transduction by a lysogenic bacteriophage.

Regarding the diagnosis of viral infections in the clinical laboratory, which one of the following provides the MOST specific diagnosis? A Cytopathic effect produced by a virus that replicates on human foreskin cells B Cytoplasmic inclusion bodies produced by a virus that replicates in the cytoplasm C Multinucleated giant cells produced by a virus that replicates in human skin cells D Neutralization of infectivity using antibody against the viral surface protein E Intranuclear inclusion bodies produced by a virus that replicates in the nucleus

D Neutralization of infectivity using antibody against the viral surface protein

Which one of the following viruses possesses a genome of single-stranded RNA that is infectious when purified? A Influenza virus B Rotavirus C Measles virus D Poliovirus

D Poliovirus

The ability of a virus to produce disease can result from a variety of mechanisms. Which one of the following mechanisms is LEAST likely? A Cytopathic effect in infected cells B Malignant transformation of infected cells C Immune response to virus-induced antigens on the surface of infected cells D Production of an exotoxin that activates adenylate cyclase

D Production of an exotoxin that activates adenylate cyclase

Rotavirus A DNA enveloped virus B DNA nonenveloped virus C RNA enveloped virus D RNA nonenveloped virus

D RNA nonenveloped virus

Regarding the mode of action of antiviral drugs, which one of the following is the MOST accurate? A Amantadine inhibits the virus-encoded DNA polymerase that is required to synthesize viral progeny DNA. B Lamivudine inhibits the cell-encoded RNA polymerase that is required to synthesize viral genome. C Raltegravir inhibits the translation of viral mRNA into viral proteins. D Ritonavir inhibits the virus-encoded protease that is required to cleave viral precursor polypeptides into functional proteins. E Zidovudine inhibits the virus-encoded RNA polymerase that is required to synthesize viral mRNA

D Ritonavir inhibits the virus-encoded protease that is required to cleave viral precursor polypeptides into functional proteins.

Many viruses mature by budding through the outer membrane of the host cell. Each of the following statements regarding these viruses is correct EXCEPT: A Some of these viruses cause multinucleated giant cell formation. B Some new viral antigens appear on the surface of the host cell. C Some of these viruses contain host cell lipids. D Some of these viruses do not have an envelope.

D Some of these viruses do not have an envelope.

Each of the following statements concerning viral serotypes is correct EXCEPT: A In naked nucleocapsid viruses, the serotype is usually determined by the outer capsid proteins. B In enveloped viruses, the serotype is usually determined by the outer envelope proteins, especially the spike proteins. C Some viruses have multiple serotypes. D Some viruses have an RNA polymerase that determines the serotype.

D Some viruses have an RNA polymerase that determines the serotype.

Many viruses are highly specific regarding the type of cells they infect. Of the following, which one is the most important determinant of this specificity? A The matrix protein B The polymerase in the virion C The protease protein D The surface glycoprotein E The viral mRNA

D The surface glycoprotein

Each of the following statements about both influenza virus and rabies virus is correct EXCEPT: A They are enveloped RNA viruses. B Their virions contain an RNA polymerase. C A killed vaccine is available for both viruses. D They each have a single antigenic type.

D They each have a single antigenic type.

Each of the following statements concerning viruses is correct EXCEPT: A Viruses can reproduce only within cells. B The proteins on the surface of the virus mediate the entry of the virus into host cells. C Neutralizing antibody is directed against proteins on the surface of the virus. D Viruses replicate by binary fission.

D Viruses replicate by binary fission.

Regarding acyclovir, which one of the following is the MOST accurate? A Bone marrow suppression is a significant adverse effect. B It terminates the latent state of both herpes simplex virus type 1 and type 2. C It inhibits the virus-encoded thymidine kinase that is required to synthesize viral DNA. D Resistance to acyclovir is primarily caused by proton pumps that export the drug from the cell. E It is a chain-terminating drug because it does not have a complete ribose ring and therefore lacks a hydroxyl group in the correct position.

E It is a chain-terminating drug because it does not have a complete ribose ring and therefore lacks a hydroxyl group in the correct position.