Microbiology Quiz 4

A virion is a(n) (a) pathogenic virus. (b) subviral particle. (c) complete, extracellular virus particle. (d) enveloped virus particle.

complete, extracellular virus particle.

An exit method used by viruses that does not immediately destroy the host bacterium is (a) lysis. (b) inversion. (c) extrusion. (d) excising

Extrusion.

The receptors to which animal virus attachment proteins usually bind are (a) proteins (b) carbohydrates. (c) nucleic acid. (d) lipids. (e) glycoproteins

Glycoproteins.

Why are viroids resistant to nucleases? (a) Having a circular RNA "genome," they are resistant to the digestion of most exonucleases (that nibble/digest the free ends of RNA or DNA). (b) Having a circular RNA "genome," with no protein shell, they are resistant to the protein-degrading activities of nucleases. (c) Nucleases will only digest DNA, not RNA-so viroids are protected. (d) Viroids have only been identified in plants. Plant nucleases cannot digest RNA.

Having a circular RNA "genome," they are resistant to the digestion of most exonucleases (that nibble/digest the free ends of RNA or DNA).

The best known chronic infection involves (a) chickenpox. (b) herpes. (c) hepatitis A. (d) hepatitis B.

Hepatitis B.

The best-known examples of viruses that cause latent infections are (a) polio. (b) herpes. (c) measles. (d) chickenpox. (e) herpes AND chickenpox

Herpes AND chickenpox

Lysogenized cells (a) are immune to any further infection by any virus. (b) are immune to infection by the same virus. (c) may have new properties. (d) respond to infection with the SOS response. (e) are immune to infection by the same virus AND may have new properties.

are immune to infection by the same virus AND may have new properties.

If the infecting phage lacks some critical pieces of DNA necessary for replication, it is called (a) incomplete. (b) mutated. (c) defective. (d) vegetative.

defective.

The approximate viral concentration of a sample may be determined by (a) quantal assay. (b) endpoint assay. (c) the titer. (d) the lysate assay.

quantal assay.

A key feature of all viral infections is the (a) integration of viral DNA into host DNA. (b) disintegration of host DNA. (c) addition of a lipid membrane to the virus. (d) separation of viral nucleic acid from the capsid.

separation of viral nucleic acid from the capsid.

The terms isometric, icosahedral and pleomorphic refer to (a) viral life cycles. (b) forms of nucleic acid. (c) types of viral envelopes. (d) shapes of viruses.

shapes of viruses

Viroids characteristically are composed of (a) ssRNA. (b) dsRNA. (c) ssDNA. (d) dsDNA.

ssRNA

During penetration of E. coli by the T4 phage (a) lysozyme is used to allow entry of the phage capsid. (b) the tail acts as a "hypodermic needle," injecting the phage DNA into the cell. (c) the protein fibers digest a hole in the cell wall. (d) the bacterial receptor molecules open a hole through the cell wall.

the tail acts as a "hypodermic needle," injecting the phage DNA into the cell.

Retroviruses are unique in that they (a) replicate in nervous system cells. (b) do not have a capsid. (c) use RNA as a template to make DNA. (d) use DNA as a template to make RNA.

use RNA as a template to make DNA.

Animal viruses are divided into a number of families whose names end in (a) -virus. (b) -viridae. (c) -viscous. (d) -eieio.

-viridae.

Diseases of short duration frequently followed by long-term immunity are referred to as (a) intermittent infections. (b) chronic infections. (c) acute infections. (d) persistent infections

Acute infections.

Prions (a) replicate by converting normal host proteins into prion proteins. (b) responsible for "mad cow disease" can cause a similar disease in humans. (c) can be transmitted by consumption of dried or cooked food. (d) that cause Spongiform Encephalopathy have the same amino acids but different folding properties from PrPc. (e) All of the above

All of the above

Why is it virtually impossible to stamp out a disease caused by a zoonotic virus? (a) You'd have to drive the vector organism extinct to do so. (b) Many vector organisms have multiple stages of their life cycle that can carry a zoonotic virus, which complicates controlling the vector-borne transmission. (c) Many viruses transmitted in this manner may utilize more than one vector organism. (d) Many zoonotic viruses may be able to reside in more than one host organism, complicating control measures. (e) All of the above are correct.

All of the above are correct.

Plant viruses may be transmitted by (a) worms. (b) contaminated seeds. (c) humans. (d) insects. (e) All of the choices are correct.

All of the choices are correct.

Viruses that infect bacteria are referred to as (a) viralcidens. (b) bacteriocidins. (c) bacterialogens. (d) bacteriophages.

Bacteriophages.

The changes that occur in virally infected cells are characteristic for a particular virus and are referred to as the (a) cytopathic effect. (b) phenotypic effect. (c) genotypic expression. (d) cytology.

Cytopathic effect.

The nucleocapsid is composed of (a) DNA and RNA and protein. (b) DNA or RNA and protein. (c) protein located in the nucleus. (d) nucleic acid in the ribosome.

DNA or RNA and protein.

The concentration of virus that infects or kills 50% of the host cells is referred to as the (a) LD50. (b) ID50. (c) ID100. (d) LD100. (e) LD50 AND ID50.

LD50 AND ID50.

Binding of this will prevent microbe to divide and make cell wall (a) Lactoferrin (b) defensin (c) Pyrogen

Lactoferrin

Phages that can either replicate and cause cell lysis or can integrate their DNA into the host DNA are called (a) lysogenic phages (b) lytic phages. (c) virulent phages. (d) segmented phages.

Lysogenic phages.

Which is a filamentous phage? (a) M13 (b) T4. (c) Lambda. (d) TMV.

M13

DNA is protected from restriction enzymes by being (a) sequestered in a lysosome (b) turned into RNA (c) methylated (d) made into double-stranded RNA

Methylated.

Would ID50 and LD50 necessarily be the same for a given virus? Why or why not? (a) Yes, because the number of viruses that infect 50% of a test population should also kill 50% of that test population. (b) No, because a virus may be highly infectious (very low ID50 value) but only marginally lethal (very high LD50 value). A prime example of this is the rhinovirus (common cold virus). (c) No, because very few viruses are lethal, yet many are highly infectious. The two values should ALWAYS be different. (d) Yes, because what we're actually describing here is infection/killing of individual CELLS, not of entire organisms. If a cell is infected, it will always be killed.

No, because a virus may be highly infectious (very low ID50 value) but only marginally lethal (very high LD50 value). A prime example of this is the rhinovirus (common cold virus).

Interferons, complement, lysozyme, and lactoferrin are all examples of (a) nonspecific antimicrobial factors. (b) specific antimicrobial factors (c) cytokines

Nonspecific antimicrobial factors

One of the most intensively studied virulent phages which infects E. coli is (a) T9 (b) T4 (c) beta (d) gamma

T4

What part of the attached bacteriophage enters through the host cell wall? (a) The entire virus (b) Only the enzymes necessary for replication (c) The nucleic acid (d) The nucleic acid and capsid (e) The capsid only

The nucleic acid

A phage that replicates inside the host cell and then lyses its host during its release is a (a) virulent or lytic phage. (b) latent phage. (c) lysogenic phage. (d) dormant phage.

Virulent or lytic phage.

The site at which a virus has infected and subsequently lysed the infected cell, releasing its progeny to infect and lyse surrounding cells, thereby forming a "clear zone," is (a) a burst area (b) a lyse area. (c) a plaque. (d) a dead zone.

a plaque.

Spongiform encephalopathy occurs in (a) humans. (b) cattle. (c) sheep. (d) all of the choices are correct.

all of the choices are correct.

In addition to lysis, animal viruses may exit the host cell by (a) extrusion. (b) budding. (c) fission. (d) fusion.

budding.

Bacteriophages and animal viruses (a) both may enter a host cell by endocytosis. (b) both may enter a host cell by fusion. (c) both involve entry of the entire nucleocapsid. (d) differ because bacteriophages leave the capsid outside the cell, while animal virus entry involves the entry of the whole nucleocapsid.

differ because bacteriophages leave the capsid outside the cell, while animal virus entry involves the entry of the whole nucleocapsid.

If reasonably pure preparations of virus are available, the number of virus present may be determined by (a) photocolorimetry. (b) gas chromatography. (c) light microscopy. (d) electron microscopy.

electron microscopy.

Enveloped viruses (a) just require a stamp. (b) have an outer lipid bilayer membrane containing various proteins. (c) are surrounded by an additional layer of carbohydrate. (d) envelope a cell.

have an outer lipid bilayer membrane containing various proteins.

Specialized transduction (a) involves the random transmission of any gene. (b) involves the transfer of a few specific genes. (c) utilizes a defective virus. (d) only involves genes near the viral DNA integration site. (e) involves the transfer of a few specific genes, utilizes a defective virus AND only involves genes near the viral DNA integration site.

involves the transfer of a few specific genes, utilizes a defective virus AND only involves genes near the viral DNA integration site.

The protein coat of a virus (a) is called a capsomere. (b) is called a capsid. (c) protects the nucleic acid. (d) is involved in the recognition of host cell receptors by non-enveloped viruses. (e) is called a capsid, protects the nucleic acid, AND is involved in the recognition of host cell receptors by non-enveloped viruses.

is called a capsid, protects the nucleic acid, AND is involved in the recognition of host cell receptors by non-enveloped viruses.

The phenomenon responsible for the ability of Corynebacterium diphtherium to produce the virulent toxin responsible for the devastating effects of diphtheria is called (a) self-assembly. (b) matrix conversion (c) prion protein. (d) lysogenic conversion

lysogenic conversion

Phage-encoded enzymes are (a) all produced simultaneously. (b) produced in a sequential manner. (c) strictly host enzymes. (d) used to customize the cell for viral production. (e) produced in a sequential manner AND used to customize the cell for viral production.

produced in a sequential manner AND used to customize the cell for viral production.