micro exam 5

The protein coat that surrounds the genetic material of the T2 phage is termed the ________. A.) envelope B.) cell wall C.) nucleoid D.) membrane E.) capsid

E.) capsid

A newly isolated virus has been analyzed for its chemical structure, and has been found to contain DNA, protein, and lipids.

Enveloped Virus

True or False In the lysogenic stage of phage replication, the host cell is lysed.

False

True or False Once a phage becomes lysogenic, it will remain lysogenic and never be lytic again.

False

True or False A naked virus fuses with host cell membrane.

False

True or False HIV leaves an infected cell by breaking down its cell membrane.

False

True or False ? Enveloped viruses are usually released from the host cell by exocytosis.

False

Rotavirus, the most common causative agent of diarrhea in infants and young children, is a member of the Reoviridae; Reoviridae is a ______ in terms of virus nomenclature.

Family

Which of the following represent(s) the way(s) in which enveloped viruses acquire their envelopes? A.) Some viruses bud through the plasma membrane while other bud through internal cellular membranes. B.) Budding through the plasma membrane. C.) Budding through internal cellular membranes. D.) Viral enzymes are responsible for production of the envelope.

Some viruses bud through the plasma membrane while other bud through internal cellular membranes.

The abnormal form of the protein is designated _________.

PrPSc

The ___________ stage in the life cycle of viruses differs greatly because of the different types of nucleic acids found in each virus.

Synthesis

Because a negative-strand RNA virus cannot function as mRNA, a ________ must accompany its entry into the host cell.

RNA-dependent RNA polymerase

A harmless PrP is converted into the infective PrP a) only as a result of a mutation in the normal gene. b) by a virus which binds to the normal protein and causes it to become misfolded. c) by an abnormal PrP which binds to the normal protein and causes it to become misfolded. d) by enzymes that break off parts of the harmless protein. e) by interaction of a PrP from one species with that of a second species.

c) by an abnormal PrP which binds to the normal protein and causes it to become misfolded.

A positive (+) strand of RNA ______.

can directly act as mRNA

Eukaryotic viruses can cause microscopic or macroscopic degenerative changes or abnormalities in host cells and in tissues that are distinct from lysis. These are called

cytopathic effects

Glycoprotein spikes protruding from the outer surface of viral envelopes function as

factors that bind to host cells.

In viral entry by endocytosis,

host plasma membrane surrounds whole virion and forms a vesicle

In phage replication ______.

only the phage nucleic acid enters the bacterial cell

The stage of T4 replication that involves the injection of phage DNA is the _____.

penetration stage

In the lytic cycle of phage replication ______.

phage nucleic acid is replicated and phage genes are expressed, making new phage protein and lysing the host cell.

A plus-strand RNA produced from a minus-strand RNA virus functions as a template for the production of ______.

negative-strand RNA genome

Single-stranded RNA viruses containing a RNA genome that is identical to mRNA are called _____ RNA viruses.

postive-strand

The first event to occur when an enveloped virus is about to exit a cell is

viral spike proteins are inserted into host cell membrane.

Which of the following requires a reverse transcriptase to produce new nucleocapsids? A.) HIV B.) Poliovirus C.) Parvovirus D.) Influenza virus

A.) HIV

Enveloped viruses are usually released from the host cell by ________.

Budding

True or False Viral nucleic acid is made inside the bacterium and is combined with viral protein coat already present outside the bacterial cell.

False

True or False Viruses with spikes usually enter host cells by endocytosis.

False

The stage of T4 replication that involves the copying of the phage DNA and the synthesis of various phage proteins is the ______.

transcription stage

A complete virus particle is called a

virion

Virus morphology does not include which of the following characteristics? A.) Size B.) Presence or absence of an envelope C.) Host range D.) Shape

C.) Host range

The stage of T4 replication that involves the protein fibers on the phage and receptors on the bacterial cell wall is the ______.

attachment stage

After the virus nucleocapsid is released from the vesicle into the host cell cytoplasm,

the capsid protein is removed

RNA-dependent RNA polymerase is an enzyme that acts as a ______________ by catalyzing the synthesis of viral mRNA. replicase ligase Incorrect primase

transcriptase

what is the proper order of the rotavirus life cycle: 1.) Formation of double-layered particles upon release from endosome 2.) Assembly within viroplasm 3.) Attachment and entry by endocytosis 4.) Uncoating and release from endosome 5.) Formation of outermost layer of virus

3,4,1,2,5

Which of the following is true of viruses in the extracellular phase? A.) They behave as a macromolecular complex and are no more alive than are ribosomes. B.) They can reproduce independently of living cells but only at a slow rate. C.) They possess many different enzymes. D.) They possess many different enzymes and they can reproduce independently of living cells but only at a slow rate.

A.) They behave as a macromolecular complex and are no more alive than are ribosomes.

Mature T2 phage particles are released A.) after lysis of the bacterial host cell. B.) by budding through the bacterial cell membrane. C.) by phagocytosis of the bacterial host cell. D.) by diffusion through the bacterial cell membrane. E.) by budding through the bacterial nuclear membrane.

A.) after lysis of the bacterial host cell.

Viral spikes A.) attach specifically to host cell receptors B.) are present in all viruses C.) are made of carbohydrate D.) attach non-specifically to host cell receptors

A.) attach specifically to host cell receptors

The stage of T4 replication that involves the protein fibers on the phage and receptors on the bacterial cell wall is the ______.

Attachment stage

Choose the answer below that defines the structure of a viroid. A.) Nucleic acid material surrounded by a phospholipid plasma membrane B.) Single-stranded RNA molecules forming a closed ring approximately 246-375 nucleotides in length C.) Nucleic acid material surrounded by a phospholipid plasma membrane and cell wall structure D.) Nucleic acid material surrounded by a protein coat E.) Protein only, with no nucleic acid or lipid components

B.) Single-stranded RNA molecules forming a closed ring approximately 246-375 nucleotides in length

The viral capsid A.) engulfs the viral spikes. B.) becomes completely enclosed by the region of the cell membrane into which the spikes and matrix protein are embedded. C.) is dissolved. D.) surrounds the viral matrix protein.

B.) becomes completely enclosed by the region of the cell membrane into which the spikes and matrix protein are embedded.

The provirus state exists when ______. A.) single-stranded RNA is present as a plasmid in the host cell B.) double-stranded viral DNA is integrated into host cell chromosome C.) single-stranded viral RNA is integrated into host cell chromosome D.) double-stranded DNA is present as a plasmid in the host cell E.) double-stranded viral RNA is integrated into host cell chromosome

B.) double-stranded viral DNA is integrated into host cell chromosome

What is the HIV protein that is involved in attachment of the virus to host cells? A.) CD4 B.) gp120 C.) CXCR-4 D.) CCR-5 E.) reverse transcriptase

B.) gp120

In the attachment step of phage replication ______. A.) carbohydrate receptors in the phage tail attach to specific receptors on the bacterial cell wall B.) protein fibers in the phage tail attach to specific receptors on the bacterial cell wall C.) phage DNA exits the protein coat and attaches to receptors on the bacterium D.) attachment is nonspecific

B.) protein fibers in the phage tail attach to specific receptors on the bacterial cell wall

A phage in the lysogenic stage can be induced to revert to the lytic stage when it undergoes A.) competition with another phage. B.) ultraviolet light treatment. C.) treatment with darkness. D.) a lack of nutrients.

B.) ultraviolet light treatment.

Choose the statement that best summarizes the characteristics of diseases caused by prions. A.) Prions cause disease in both animals and a number of plant species; all disease results in death of the host. B.) Prions cause progressive degeneration of the brain which can be treated using interferon therapy. C.) All result in progressive degeneration of the brain and eventual death. At present, no effective treatment exists. D.) All result in progressive degeneration of the peripheral nervous system and eventual death. At present, no effective treatment exists.

C.) All result in progressive degeneration of the brain and eventual death. At present, no effective treatment exists.

Lysogenic conversion of which bacterial species by phage β results in increased pathogenicity of the bacteria?

Corynebacterium diphtheriae.

The ________ dose is the dose that causes 50% of the host organisms to become infected.

Infection

Release of nonenveloped viruses occurs most often by _________.

Lysis

True or False Attachment of HIV to a host cell requires a receptor and co-receptor on the surface of the host cell.

True

True or False Viral lysozyme digests the host cell wall, releasing the newly made phage, and lysing the host cell in the release step.

True

True or False It is hard to create a vaccine against HIV infection because the virus has a high mutation rate.

True

True or False Phage T2 infection of a bacterial cell is accompanied by degradation of host cell DNA.

True

True or False ? A phage induced lysozyme lyses the host cell releasing the newly made phage.

True

True or False ? A portion of the viral envelope comes from the cell membrane of the host cell.

True

True or False? Disease symptoms are believed to be the result of dense aggregates of the abnormal protein.

True

True or false? The enzyme lysozyme is used by the T4 phages to enter the host cell.

True

Viruses that consist of a protein capsid containing nucleic acid are referred to as _________.

naked virus

In positive-sense strand RNA phage, the negative (-) sense strand of RNA ______.

is used to synthesize more + strands

Single-stranded RNA viruses containing RNA sequences that are complementary to the mRNA produced upon their infection of a host cell are called _____ RNA viruses.

minus-strand or negative-strand

In the attachment step of phage replication ______.

protein fibers in the phage tail attach to specific receptors on the bacterial cell wall

RNA-dependent RNA polymerase is an enzyme that acts as a _____ by catalyzing the synthesis of plus-strand RNA.

replicase

True or False? Viral lysozyme digests the host cell wall, releasing the newly made phage, and lysing the host cell in the release step.

True

Because the size range of virions is from _______ in diameter, they cannot be seen using a _______________ microscope. A.) 10 to 400 nm; bright-field (light) B.) 10 to 400 pm; bright-field (light) microscope C.) 10 to 400 cm; scanning electron microscope D.) 10 to 400 nm; electron

A.) 10 to 400 nm; bright-field (light)

Chemokines appear to inhibit HIV infection by ______. A.) blocking the CXCR4 and CCR5 coreceptors B.) interfering with the cleavage of viral polyproteins C.) blocking replication of the virus D.) interfering with the synthesis of viral proteins E.) disabling the CD4 receptor

A.) blocking the CXCR4 and CCR5 coreceptors

Choose the statement that is true about West Nile disease. A.) Ticks harbor the greatest concentration of West Nile virus in the late summer and early fall. B.) WNV is transmitted predominately to humans by ticks that feed on infected birds (crows and sparrows). C.) In West Nile disease, there is a peak of infection in late August and early September and most infected individuals exhibit only mild flu-like symptoms. D.) Although many people are bitten by WNV-infected mosquitoes, most infected individuals exhibit only mild, flulike symptoms. E.) In West Nile disease, there is a peak of disease in late August to early September.

C.) In West Nile disease, there is a peak of infection in late August and early September and most infected individuals exhibit only mild flu-like symptoms.

Which of the following is NOT a mechanism that a virus could use to generate many rather than one single protein? A.) While reading the viral mRNA, host ribosomes pause and then shift to a new reading frame. B.) Translation is initiated within different sites within the mRNA, each encoding for a different protein. C.) Viruses release cell signals upon entry that initiate translation for each particular protein. D.) One long protein is produced, which is cleaved by enzymes into the needed proteins. E.) Ribosome reads through a stop codon to generate a larger protein.

C.) Viruses release cell signals upon entry that initiate translation for each particular protein.

Which of the following viral diseases is not spread through airborne transmission? A.) Chickenpox B.) Measles C.) West Nile fever D.) Influenza

C.) West Nile fever

Hemagglutinin found in the influenza virus functions to ______. A.) stimulate the budding of newly assembled viral particles B.) produce a new viral genome C.) control the binding of the virus to host cell receptors D.) hydrolyze the mucus produced by epithelial cells

C.) control the binding of the virus to host cell receptors

If the DNA of the provirus is transcribed ______. A.) the provirus detaches and becomes lytic B.) a plasmid is made C.) one long polygenic mRNA is produced D.) several single mRNA strands are produced

C.) one long polygenic mRNA is produced

In phage replication ______. A.) the whole phage particle enters the cell and the protein outer coat is removed B.) only the phage protein enters the bacterial cell C.) only the phage nucleic acid enters the bacterial cell D.) multiple phage particles enter the same host bacterial cell at the same time

C.) only the phage nucleic acid enters the bacterial cell

A prophage is A.) phage DNA being actively expressed. B.) toxic to the host bacterial cell. C.) phage DNA integrated into host cell genome. D.) phage protein left outside the bacterium.

C.) phage DNA integrated into host cell genome.

In the lytic cycle of phage replication, A.) phage genes exist as prophage. B.) phage genes integrate into the host cell genome and are not expressed. C.) phage nucleic acid is replicated and phage genes are expressed, making new phage protein and lysing the host cell. D.) phage DNA remains inside the protein coat.

C.) phage nucleic acid is replicated and phage genes are expressed, making new phage protein and lysing the host cell.

In the replication of the positive (+) sense strand of lytic RNA phage, in order to make more positive (+) strands A.) the RNA replicase uses the (+) sense RNA as a template to make (-) strand RNA. B.) the (+) RNA strand must code for the synthesis of RNA polymerase (replicase). C.) the (-) sense strand RNA is used to make more (+) strands. D.) All of the choices are correct.

D.) All of the choices are correct.

An antiviral factor called ________ has been found in ________ cells. A.) CAF; CD4 B.) NEF; CD8 C.) NEF; brain D.) CAF; CD8 E.) NEF; CD4

D.) CAF; CD8

Which of the following is mismatched? A.) Variant Creutzfeldt-Jakob disease - consumption of nervous tissue from cows with BSE B.) Gerstmann-Sträussler-Scheinker disease (GSD) - inherited genetic disorder C.) Fatal familial insomnia - inherited genetic disorder D.) Creutzfeldt-Jakob disease - transmitted through cannabalism

D.) Creutzfeldt-Jakob disease - transmitted through cannabalism

What part of the phage enters the bacterial cell following infection? A.) RNA B.) The entire phage C.) Protein coat D.) DNA E.) No part

D.) DNA

Choose the answer below that is not a human disease caused by prions. A.) Kuru B.) Fatal familial insomnia C.) Creutzfeldt-Jakob disease D.) Scrapie

D.) Scrapie

The drug AZT ______. A.) binds to human cell receptors thereby blocking HIV's access to them B.) inhibits the enzyme protease C.) inhibits the production of HIV proteins D.) inhibits the enzyme reverse transcriptase E.) breaks down human cell receptors so that HIV cannot bind to them

D.) inhibits the enzyme reverse transcriptase

The type of cells infected by HIV are ________ early in the course of an infection and ________ late in the infection. A.) macrophages; helper B cells B.) helper T cells; cytotoxic T cells C.) helper T cells; macrophages D.) macrophages; helper T cells E.) macrophages; cytotoxic T cells

D.) macrophages; helper T cells

Prions are believed to cause ________ diseases a) Respiratory b) Digestive c) Sexually-transmitted d) Neurodegenerative e) Plant

D.) neurodegenerative

The HIV enzyme that makes a double-stranded DNA copy of the viral genome is ______. A.) gyrase B.) RNA polymerase C.) endonuclease D.) reverse transcriptase E.) DNA polymerase

D.) reverse transcriptase

Retroviruses have ______. A.) one copy of double-stranded RNA B.) two copies of single-stranded DNA C.) one copy of single-stranded RNA D.) two copies of single-stranded RNA

D.) two copies of single-stranded RNA

True or False ? Viral nucleic acid is made inside the bacterium and is combined with viral protein coat already present outside the bacterial cell.

False

True or False? If the virus is present as a provirus in the host cell, it remains latent and never produces new virus.

False

True or False? During the transcription stage, the phage DNA merges with the host DNA.

False

True or False? In the lysogenic stage of phage replication, the host cell is lysed.

False

True or False? In some inherited cases, the normal prion protein can convert spontaneously to the abnormal form, but at a slow rate.

True

True or False? The polygenic mRNA codes for one long polyprotein that is cleaved into the separate individual virus proteins.

True