question

we sometimes are able to generate antibodies (immune system proteins) that bind to and cover up some of the proteins on the outermost portion of a virus while it is in the bloodstream. this renders the virus unable to reproduce. which step of viral replication are antibodies directly preventing?

answer

attachment

question

enveloped viruses have a layer of lipids surrounding their capsid. this envelope is made mostly of host cell membrane. in which step does the virus acquire this envelope?

answer

release - during budding release, the virus "steals" some of the host membrane to use for itself

question

what occurs during viral uncoating?

answer

the capsid breaks apart, releasing the viral genome

question

viral replication process

answer

1. requires viral attachment sites and host cell surface receptors 2. may occur via fusion or via receptor-mediated endocytosis 3. makes copies of viral nucleic acid and viral proteins 4. assembly of new viruses 5. may involve budding (enveloped viruses) or lysis of host cell (noneveloped viruses)

question

what happens in each step of the viral replication process

answer

1. attachment - requires a physical and chemical interaction between the surface of the virus and host cell surface 2. entry and uncoating - may involve receptor - mediated endocytosis, may involve fusion of the viral envelope with the host cell plasma membrane, and this process disassembles the viral capsid and releases the viral DNA 3. biosynthesis - the viral DNA must enter the host cell nucleus prior to this stage, transcription of viral genes by host cell RNA polymerase occurs during this stage, new copies of viral DNA genomes are made during this stage, and translation of viral capsid proteins and other viral proteins occurs during this stage 4. maturation - viral genomic DNA is packed into newly assembled capsids and capsids are assembled from capsomeres 5. release - noneveloped viruses often lyse the cell during this process and enveloped viruses accomplish this via a budding process

question

What are some possible consequences of the specific interaction between viral attachment sites and host cell surface receptors?

answer

-viral infection of a cell may be prevented by blocking the attachment site on a virus with antibody -viral infection of a cell may be prevented by blocking the receptor sites on a host cell -some people are naturally (innately) resistant to certain viral infections -a particular virus may be able to infect humans but not mice -a particular virus may be able to infect a liver cell but not a lung cell

question

a viroid is a(n)

answer

infectious piece of RNA without a capsid

question

which of the following statements about viral spikes is FALSE? a. they are composed of carb-protein complexes b. they may cause hemagglutination c. they are found only on noneveloped viruses d. they are used for attachment e. they bind to receptors on the host cell surface

answer

c. they are found only on noneveloped viruses

question

viruses that utilize reverse transcriptase belong to the virus families

answer

hepadnaviridae and retroviridae

question

a clear area against a confluent "lawn" of bacteria is called a

answer

plaque

question

an example of a latent viral infection is

answer

cold sores

question

a virus's ability to infect an animal cell depends primarily upon the

answer

presence of receptor sites on the cell membrane

question

what would be the first step in biosynthesis of a virus with a - (minus) strand of RNA?

answer

synthesis of double-stranded RNA from an RNA template

question

which one of the following steps does NOT occur during multiplication of a picornavirus? a. synthesis of DNA b. synthesis of - strands of RNA c. synthesis of viral proteins d. synthesis of + strands of RNA e. none of the answers are correct

answer

a. synthesis of DNA

question

which of the following statements concerning viruses is true? a. viruses possess enzymes for protein synthesis and ATP generation b. viruses contain both DNA and RNA, and they undergo binary fusion c. 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 d. viruses are usually about the same size as bacteria

answer

C. the "host range" for a virus is determine by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach - attachment of the virus to the host cell (the first step in the viral life cycle) requires binding of complementary molecules on the virus and host cell

question

what statement provides the most significant support for the idea that viruses are nonliving chemicals

answer

they are not composed of cells

question

how do all viruses differ from bacteria?

answer

viruses are not composed of cells

question

which of the following statements about viruses is FALSE? a. viruses use the anabolic machinery of the cell b. viruses use their own catabolic enzymes c. viruses contain DNA or RNA but never both d. viruses contain a protein coat e. viruses have genes

answer

b. viruses use their own catabolic enzymes

question

which statement concerning viral structure is true? a. spikes are found on some viruses. they are very consistent in structure and can be used for identification b. the proteins in the envelope are capsomeres c. animal viruses usually contain tail sheaths and spikes d. all viruses contain an envelope, which is made of lipid, carb, and protein

answer

a. spikes are found on some viruses. they are very consistent in structure and can be used for identification - some enveloped viruses have spikes, and they can be used for identification, such as the H and N spikes on the influenza virus

question

true/false: a viroid is a completely developed infectious agent composed of nucleic acid and surrounded by a capsid

answer

false

question

true/false: viruses are the only known infectious agents that are obligatory intracellular parasites

answer

false - viruses are obligatory intracellular parasites -- so they must have evolved after a suitable host cell had evolved.

question

true/false: helical and icosahedral are terms used to describe the shapes of a virus envelope

answer

false

question

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

answer

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

question

what contributes to antigenic shift in influenza viruses?

answer

a segmented genome

question

what is NOT utilized to culture viruses?

answer

culture media

question

continuous cell lines differ from primary cell lines in that

answer

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

question

true/false: a segmented genome can result in antigenic shift

answer

true

question

which statement is CORRECT concerning animal viruses? a. the genome of animal viruses is always single-stranded b. enveloped viruses are surrounded by a lipid and carb coat, which is made from the host cell's mitochondria c. retroviruses use an enzyme called reverse transcriptase, which synthesizes DNA by copying RNA d. capsid proteins are produce in the nucleus

answer

c. retroviruses use an enzyme called reverse transcriptase, which synthesizes DNA by copying RNA - retroviruses have an RNA genome that is converted to DNA inside a host cell by viral reverse transcriptase

question

how are viruses different from cells?

answer

they require a host in order to reproduce

question

what is the function of the structural elements of a virus?

answer

to package and protect the viral genome

question

which of the following statements is NOT true of lysogeny? a. it can give infected pathogens the genetic info for toxin production b. it is a "silent" infection; the virus does not replicate c. prophage is inserted into the host genome d. lytic cycle may follow lysogeny e. it causes lysis of host cells

answer

e. it causes lysis of host cells

question

generally, in an infection caused by a DNA-containing virus, the host animal cell supplies all of the following except a. nucleotides b. DNA polymerase c. RNA polymerase d. tRNA e. none of the answers are correct; all of these are supplied by the host animal cell

answer

b. DNA polymerase

question

DNA-virus replication in order

answer

DNA synthesis, transcription, translation, and maturation

question

the following steps occur during multiplication of herpesviruses. which is the third step?

answer

uncoating

question

the following steps occur during multiplication of retroviruses. which is the fourth step?

answer

synthesis of double-stranded DNA

question

most RNA viruses carry which of the following enzymes? a. RNA-dependent RNA polymerase b. lysozyme c. ATP synthase d. DNA-dependent DNA polymerase e. reverse transcriptase

answer

a. RNA-dependent RNA polymerase

question

true/false: positive sense RNA strands of viruses are treated like mRNA inside the host cell

answer

true

question

the mechanism whereby an enveloped virus leaves a host cell is called

answer

budding

question

_________ were first identified in cancer-causing viruses and can induce ________ in infected cells

answer

oncogenes; transformation

question

which virus is NOT associated with cancer? a. human papillomavirus (HPV) b. coronavirus c. hepatitis B virus (HBV) d. epstein-barr virus (EBV)

answer

b. coronavirus

question

some viruses, such as human herpesvirus 1, infect a cell without causing symptoms. these are called

answer

latent viruses

question

what human disease is caused by prions?

answer

creutzfeldt-jakob disease (CJD) - a spongiform encephalopathy, is the only human disease listed that is caused by proteinaceous infectious particles (prions)

question

which of the following statements concerning prion diseases is true? a. prion diseases are always inherited b. prion diseases affect humans but not other animals c. normal host cellular prion proteins are converted into scrapie proteins d. prion diseases affect brain function but do not affect the morphology (overall appearance) of brain tissues

answer

c. normal host cellular prion proteins are converted into scrapie proteins

question

which of the following is true of viroids? a. there are similarities bw the base sequences of viroids and exons, resulting in the hypothesis that viroids evolved from exons b. viroids are short pieces of naked RNA c. viroids are typically extremely long and contain numerous genes d. viroid is the term for a virus that infects plants

answer

b. viroids are short pieces of naked RNA

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