Micro CH.13

In what year did Stanley Prusiner discover prions? 1979 1982 1928 1997

1982

Which of the following is most likely a product of an early gene? spike proteins DNA polymerase capsid proteins lysozyme envelope proteins

DNA polymerase

A viroid is a completely developed infectious agent composed of nucleic acid and surrounded by a capsid. T/F

FALSE

Glycoprotein spikes are found on the capsids of all viruses. T/F

FALSE

Helical and icosahedral are terms used to describe the shapes of a virus envelope. T/F

FALSE

Viruses are the only known infectious agents that are obligatory intracellular parasites. T/F

FALSE

DNA made from an RNA template will be incorporated into the virus capsid of.......... influenzavirus. Retroviridae. Hepadnaviridae. Herpesviridae. bacteriophage families.

Hepadnaviridae.

________ were first identified in cancer-causing viruses and can induce ________ in infected cells. Herpes viruses; lesions Oncogenes; transformation Segmented genomes; reassortment T antigens; lysis Glycoprotein spikes; syncytia formation

Oncogenes; transformation

Which of the following is necessary for replication of a prion? lysozyme PrPSc DNA DNA polymerase RNA

PrPSc

Which disease did Stanley Prusiner first identify as being caused by prions? Mad cow disease Fatal familial insomnia Scrapie Kuru

Scrapie

Dogs do not get measles because their cells lack the correct receptor sites for that virus. T/F

TRUE

Most drugs that interfere with viral multiplication also interfere with host cell function. T/F

TRUE

Positive sense RNA strands of viruses are treated like mRNA inside the host cell. T/F

TRUE

The basic mechanism of viral multiplication is similar for all viruses. T/F

TRUE

Which of the following statements about viral spikes is FALSE? They bind to receptors on the host cell surface. They are composed of carbohydrate-protein complexes. They are used for attachment. They are found only on nonenveloped viruses. They may cause hemagglutination.

They are found only on nonenveloped viruses.

Which of the following statements provides the most significant support for the idea that viruses are nonliving chemicals? They are not composed of cells. They are filterable. They cause diseases similar to those caused by chemicals. They are chemically simple. They cannot reproduce themselves outside a host.

They are not composed of cells.

How do all viruses differ from bacteria? Viruses do not reproduce. Viruses are obligate intracellular parasites. Viruses do not have any nucleic acid. Viruses are filterable. Viruses are not composed of cells.

Viruses are not composed of cells.

Which of the following is NOT used as a criterion to classify viruses? biochemical tests size nucleic acid number of capsomeres morphology

biochemical tests

Bacteriophages and animal viruses do NOT differ significantly in which one of the following steps? release biosynthesis penetration attachment uncoating

biosynthesis

The mechanism whereby an enveloped virus leaves a host cell is called........... transduction. lysogeny. penetration. budding. abduction.

budding.

Oncogenic viruses........ cause acute infections. are lytic viruses that kill the host cell. are genetically unstable. cause tumors to develop. have no effect on the host cell.

cause tumors to develop.

A viroid is a(n)............. capsid without nucleic acid. infectious protein. provirus. complete, infectious virus particle. infectious piece of RNA without a capsid.

infectious piece of RNA without a capsid.

Bacteriophages derive all of the following from the host cell EXCEPT.................. amino acids. lysozyme. nucleotides. tRNA. ATP.

lysozyme.

A clear area against a confluent "lawn" of bacteria is called a.............. plaque. cell lysis. pock. phage. rash.

plaque.

A virus's ability to infect an animal cell depends primarily upon the................. type of viral nucleic acid. host cell's ability to phagocytize viral particles. presence of pili on the host cell wall. presence of receptor sites on the cell membrane. enzymatic activity of a host cell.

presence of receptor sites on the cell membrane.

An infectious protein is a.............. papovavirus. viroid. retrovirus. bacteriophage. prion.

prion.

An envelope is acquired during which of the following steps? penetration adsorption uncoating biosynthesis release

release

Which one of the following steps does NOT occur during multiplication of a picornavirus? synthesis of DNA synthesis of + strands of RNA synthesis of viral proteins synthesis of - strands of RNA None of the answers is correct.

synthesis of DNA

Assume you have isolated an unknown virus. This virus has a single, positive sense strand of RNA, and possesses an envelope. To which group does it most likely belong? herpesvirus picornavirus papovavirus retrovirus togavirus

togavirus

The following steps occur during multiplication of herpesviruses. Which is the third step? biosynthesis release penetration attachment uncoating

uncoating

Which statement is CORRECT concerning animal viruses? • Retroviruses use an enzyme called reverse transcriptase, which synthesizes DNA by copying RNA. •Capsid proteins are produced in the nucleus. • Enveloped viruses are surrounded by a lipid and carbohydrate coat, which is made from the host cell's mitochondria. • The genome of animal viruses is always single-stranded

• Retroviruses use an enzyme called reverse transcriptase, which synthesizes DNA by copying RNA.

Which of the following places these items in the correct order for DNA-virus replication? 1. Maturation 2. DNA synthesis 3. Transcription 4. Translation ---------------------------------------------------- •3; 4; 1; 2 •4; 3; 2; 1 •2; 3; 4; 1 •1; 2; 3; 4 •4; 1; 2; 3

•2; 3; 4; 1

Which of the following is a human disease caused by prions? •shingles •Creutzfeldt-Jakob disease (CJD) •subacute sclerosing panencephalitis (SSPE) •chickenpox (varicella)

•Creutzfeldt-Jakob disease (CJD)

Generally, in an infection caused by a DNA-containing virus, the host animal cell supplies all of the following EXCEPT..... •DNA polymerase. •RNA polymerase. •tRNA. •nucleotides. •None of the answers are correct; all of these are supplied by the host animal cell.

•DNA polymerase.

Which of the following is true regarding cultivation and isolation of animal viruses? •Viruses can be easily grown in liquid culture without any other organisms present. •Mouse models are available for virtually all human viral infections and can be routinely used for vaccine development. •The preferred and widely used method of viral isolation and growth is via growth in an embryonated egg. •Diploid cell culture lines, developed from human embryos, are widely used for culturing viruses that require a human host.

•Diploid cell culture lines, developed from human embryos, are widely used for culturing viruses that require a human host.

Which of the following is true concerning a lysogenic viral replication cycle? •During lysogeny, the viral DNA is present as a circular plasmid. •Once the lysogenic portion of the cycle has begun, virus is never produced again. •Lysogenic infections are similar to persistent infections in that virus is constantly produced. •During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome.

•During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome.

Viruses that utilize reverse transcriptase belong to the virus families................. •Retroviridae and Picornaviridae. •Herpesviridae and Retroviridae. •Rhabdoviridae and Herpesviridae. •Hepadnaviridae and Retroviridae. •Herpesviridae and Poxviridae.

•Hepadnaviridae and Retroviridae.

Which of the following statements is NOT true of lysogeny? •It is a "silent" infection; the virus does not replicate. •It causes lysis of host cells. •Lytic cycle may follow lysogeny. •It can give infected pathogens the genetic information for toxin production. •Prophage is inserted into the host genome.

•It causes lysis of host cells.

Which of the following statements regarding latent viral infections is true? •Latent viral infections are caused by the slow conversion of cellular glycoproteins from normal to infectious form. •During latent infections, small amounts of virus are produced, and virus numbers build up over time. •Latent infections can persist for years in an individual without causing any symptoms. •Latent viral infections are almost always fatal.

•Latent infections can persist for years in an individual without causing any symptoms.

Which of the following statements concerning prion diseases is true? •Prion diseases are always inherited. •Prion diseases affect brain function but do not affect the morphology (overall appearance) of brain tissues. •Normal host cellular prion proteins (PrPC) are converted into scrapie proteins (PrPSc). •Prion diseases affect humans but not other animals.

•Normal host cellular prion proteins (PrPC) are converted into scrapie proteins (PrPSc).

From which phrase is the term "prions" derived? •Particles of infection •Protein infections •Proteinaceous infectious particles •Protein infection of the nervous system

•Proteinaceous infectious particles

Most RNA viruses carry which of the following enzymes? •RNA-dependent RNA polymerase •DNA-dependent DNA polymerase •ATP synthase •lysozyme •reverse transcriptase

•RNA-dependent RNA polymerase

Which statement concerning viral structure is true? •Spikes are found on some viruses. They are very consistent in structure and can be used for identification. •Animal viruses usually contain tail sheaths and spikes. •The proteins in the envelope are capsomeres. •All viruses contain an envelope, which is made of lipid, carbohydrate, and protein.

•Spikes are found on some viruses. They are very consistent in structure and can be used for identification.

Which of the following statements concerning viruses is true? •The "host range" for a virus is determined by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach. •Viruses are usually about the same size as bacteria. •Viruses contain both DNA and RNA, and they undergo binary fusion. •Viruses possess enzymes for protein synthesis and ATP generation.

•The "host range" for a virus is determined by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach.

Which of the following statements is FALSE? •Prophage genes are repressed by a repressor protein coded for by the prophage. •The prophage makes the host cell immune to infection by other phages. •A prophage is phage DNA inserted into a bacterial chromosome. •A prophage can "pop" out of the chromosome. •A prophage may result in new properties of the host cell.

•The prophage makes the host cell immune to infection by other phages.

A lytic virus has infected a patient. Which of the following would best describe what is happening inside the patient? •The virus is causing the death of the infected cells in the patient. •The virus is incorporating its nucleic acid with that of the patient's cells. •The virus is not killing any cells in the host. •The virus is slowly killing the patient's cells. •The virus is infecting cells and then releasing only small amounts of virus.

•The virus is causing the death of the infected cells in the patient.

How are prions different from other infectious agents? •They cannot replicate. •They lack nucleic acid. •They lack protein. •They cause neurological disease

•They lack nucleic acid.

Which of the following statements about viruses is FALSE? •Viruses use their own catabolic enzymes. •Viruses contain DNA or RNA but never both. •Viruses use the anabolic machinery of the cell. •Viruses contain a protein coat. •Viruses have genes.

•Viruses use their own catabolic enzymes.

The most conclusive evidence that viruses cause cancers is provided by................ •treating cancer with antibodies. •cancer following injection of cell-free filtrates. •the presence of antibodies against viruses in cancer patients. •finding oncogenes in viruses. some liver cancer patients having had hepatitis.

•cancer following injection of cell-free filtrates.

An example of a latent viral infection is...... •subacute sclerosing panencephalitis. •influenza. •mumps. •smallpox. •cold sores.

•cold sores.

Continuous cell lines differ from primary cell lines in that......... •continuous cell lines are from human embryos. •continuous cell lines always have to be re-isolated from animal tissues. •continuous cell lines can be maintained through an indefinite number of generations. •continuous cell lines are derived from primary cell lines. •viruses can be grown in continuous cell lines.

•continuous cell lines can be maintained through an indefinite number of generations.

Which virus is NOT associated with cancer? •human papillomavirus (HPV) •coronavirus •hepatitis B virus (HBV) •Epstein-Barr virus (EBV)

•coronavirus

Lysogeny can result in all of the following EXCEPT........... •acquisition of new characteristics by the host cell. •specialized transduction. •immunity to reinfection by the same phage. •phage conversion. •immunity to reinfection by any phage.

•immunity to reinfection by any phage.

Bacteriophage replication differs from animal virus replication because only bacteriophage replication involves....... •assembly of viral components. •adsorption to specific receptors. •lysis of the host cell. •replication of viral nucleic acid. •injection of naked nucleic acid into the host cell.

•injection of naked nucleic acid into the host cell.

The definition of lysogeny is............... •when the burst time takes an unusually long time. •phage DNA is incorporated into host cell DNA. •lysis of the host cell due to a phage. •attachment of a phage to a cell. •the period during replication when virions are not present.

•phage DNA is incorporated into host cell DNA.

The following steps occur during multiplication of retroviruses. Which is the fourth step? •penetration •attachment •uncoating •synthesis of +RNA •synthesis of double-stranded DNA

•synthesis of double-stranded DNA

Which of the following would be the first step in biosynthesis of a virus with a - (minus) strand of RNA? •synthesis of DNA from an RNA template •synthesis of double-stranded RNA from a DNA template •synthesis of DNA from a DNA template •transcription of mRNA from DNA •synthesis of double-stranded RNA from an RNA template

•synthesis of double-stranded RNA from an RNA template

The following steps occur during biosynthesis of a + strand RNA virus. What is the third step? •synthesis of - strand RNA •attachment •penetration and uncoating •synthesis of viral proteins •synthesis of + strand RNA

•synthesis of viral proteins

A persistent infection is one in which.................... •the virus remains in equilibrium with the host without causing a disease. •host cells are gradually lysed. •the disease process occurs gradually over a long period. •viral replication is unusually slow. •host cells are transformed.

•the disease process occurs gradually over a long period.