Chapter 25 Microbiology

________ mRNA is synthesized before replication of the viral nucleic acid.  

Bacteriophage T4 blocks transcription of host genes using an enzyme that transfers an ______ from NAD onto the alpha subunit of RNA polymerase.  

__________ is an unusual base found in the DNA of T-even phages.  

When a _________ enters a host cell, it loses the outermost protein layer and is then referred to by virologists as a double-layered particle (DLP).  

After infecting the cell, HBV's gapped DNA is released into the nucleus where host _______ enzymes fill the gap and seal the nick, yielding a covalently closed, circular DNA  

 Influenza virus adheres to the epithelium of the respiratory system with the aid of _________ and _________ found in its envelope spikes.   (answer, answer)  

One way in which small viruses package more information into a very small genome is to use overlapping genes so that the same base sequence is read in more than one reading frame.  

• True

• False

In the case of phage lambda, termination of lysogeny and entry into the lytic cycle usually occurs in response to environmental damage to the host DNA.  

• True

• False

Glucosylation of hydroxymethylcytosine residues protects phage T4 DNA from cleavage by bacterial restriction enzymes.  

• True

• False

 Segmented genomes in negative-strand RNA viruses may have evolved from unsegmented ones; they may have been created by the reduction of redundant genetic regions.  

• True

• False

 Parvoviruses are among the simplest known DNA viruses of animals.  

• True

• False

Tobacco mosaic virus can be transmitted between individual plants by biting insects.  

• True

• False

Although poliovirus capsids contain several distinct proteins, these are synthesized as a single polypeptide then cleaved by proteases to produce the individual proteins.  

• True

• False

Which of the following is(are) used in the classification of animal viruses?  

• Virion morphology

• genome structure

• Genetic relatedness

• All of the choices

Viruses infecting algae have never been detected.  

• True

• False

 A __________ infection is one in which the virus quits reproducing and remains dormant for a period before becoming active again.  

• Persistent

• Latent

• Slow virus

• None of these

Hepatitis B virus is an example of a DNA virus that uses reverse transcriptase in its replication cycle.  

• True

• False

 For most T-even phages, the nucleic acid enters the host cell but the capsid is left outside.  

• True

• False

 Almost all known plant viruses are RNA viruses.  

• True

• False

The most common type of molecule found on the surface of animal viruses for interacting with host cell receptors is a(n)  

• Lipoprotein

• Glycoprotein

• Phosphoprotein

• Teichoic acid

Once a virus establishes lysogeny, it may not switch to the lytic cycle at some later time.  

• True

• False

Bacteriophage that only exhibit lytic replication cycles are called __________ phages.  

• Temperate

• Virulent

• Intemperate

• Lytigate

Virus morphology does not include which of the following characteristics?  

• Size

• Shape

• presence or absence of an envelope

• Host range

In T-even phages, which of the following makes the initial contact with the appropriate receptor site?  

• Tail fiber

• Base plate

• Collar

• Tail tube

Because their host cells have dsDNA genomes, viruses with RNA genomes cannot rely on host cell enzymes for genome replication or mRNA synthesis.  

• True

• False

The protein required for the establishment and maintenance of lysogeny in cells infected with the temperate bacteriophage lambda is the  

• Lac repressor.

• Lambda repressor.

•  lambda cos.

• Lambda Xis and Int proteins.

A group of viruses that cause severe diarrhea, resulting in over 600,000 deaths worldwide annually is the  

• Polioviruses

• Rotaviruses

• Poxviruses

• Herpesviruses

 Entry of a virus into the lytic cycle after lysogeny has been established is called  

• Lysogenic conversion.


•  lysogenic reversion.

• Induction

• None of the choices

Phage T4 protects its DNA from cleavage by host restriction enzymes by  

• Inactivating restriction enzymes.

•  substituting glucosylated hydroxymethylcytosine for cytosine.


• Methylating bases.


• Replicating very rapidly.

A _________________ is a sequence-specific recognition protein with endonuclease activity.  

• DNA Helicase

• Terminal transferase

• Restriction endonuclease 


• DNA ligase

Unlike most enveloped viruses, herpes viruses involve the host __________ membrane in the formation of their envelope.  

• Plasma

• Nuclear

• Mitochondrial

• None of these

A bacteriophage that can integrate its genome into the host chromosome and not cause lysis of the host cell is said to be  

• Virulent

• Avirulent

• Moderate

• Temperate

The tails of some bacteriophage  

• include a contractile sheath.

• rotate like flagella to drive the phage genome into the cytoplasm of the host.

• Exhibit oar like motion that drives the phage genome into the cytoplasm of the host.

• None of the choices

Which of the following represent(s) the way(s) in which enveloped viruses acquire their envelopes?  

• Budding through the plasma membrane.


•  budding through internal cellular membranes.


• Viral enzymes are responsible for production of the envelope.


• For some viruses, a is correct; for other viruses, b is correct.

The largest viruses known are the  

• Herpes viruses

• Hepadnaviruses

• Adenoviruses

• Mimiviruses

The latent form of a bacteriophage genome that exists when a phage establishes lysogeny is called a  

• Lysogen

• Prophage

• Viroid

• Prion

Establishment of lysogeny by phage is usually influenced strongly by  

• The previous host infected by the virus.


• Components of the host replication machinery.

• The physiological condition of the host at the time of infection.


• None of the choices

Attachment of a bacteriophage to its host requires  

•   specific surface proteins on the bacteriophage. 


• Specific receptor molecules on the host cell.

• Nucleic acid protein interactions. 


• Specific surface proteins on the bacteriophage and specific receptor molecules on the host cell

In order for bacteriophage to be released from the host by a lysis mechanism, enzymes are required that  

•   halt ATP synthesis.

• Stabilize the cytoplasmic membrane and cell wall. 


• Damage the cell wall and cytoplasmic membrane.

• Degrade the host chromosome.

Which of the following uses ssDNA as the genome?  

• Parvovirus

• Poliovirus

• Herpesvirus

• Poxvirus

Which of the following does not use RNA as the genome?  

• Poxvirus

• Poliovirus

• Influenza virus

• Rabies virus

In which of the following stages of the viral infectious cycle do enveloped viruses usually acquire their envelopes?  

• Penetration

• Component biosynthesis

• Assembly

• Release

_____________ are able to degrade infecting bacteriophage DNA, thus protecting the host cell.  

• Lysozyme

• Protection exonucleases


• Restriction endonucleases

• Modification methylases

Which of the following is not a function of the replicative form (dsDNA) of phage phiX174?  

• Direct the synthesis of more RF copies


• Direct the synthesis of minus-stranded DNA

• Direct the synthesis of plus-stranded DNA


• Direct the synthesis of mRNA

All bacteriophages infecting members of the Archaea possess genomes made of  

• DsDNA

• SsDNA

• DsRNA

• SsRNA

 The cascade of events determining whether bacteriophage lambda elects to purpose lysogeny or a lytic cycle begins with a race between the production of the lambda repressor and  

• Integrase

• N protein.

• Endolysin

• Cro protein.

 Release of T4 phage from host cells after assembly  

• Occurs by extrusion and does not result in cell lysis.

• Depends on a protein that interacts with MurA and interferes with normal peptidoglycan synthesis.

• Requires holin protein which allows the T4 lysozyme to attack the peptidoglycan.

• Occurs by exocytosis.

The sequence of genes in each T4 virus within a population is the same but starts with a different gene at the 5' end. If each of these linear pieces is circularized, the gene sequences would be identical. The T4 DNA, therefore, is described as being  

• Two fold rotationally symmetrical.

• A linear repeat.


• Circularly permuted.

• Linearly palindromic.