Microbiology Chapter 13

Replication of temperate phages and lytic phages have which steps in common?

Biosynthesis of viral components, release, genome entry, assembly, attachment

Which of the following viral release methods may not initially destroy the cell?

Budding

Which fact best supports the position that viruses are not living organisms?

Viruses cannot reproduce on their own

Match the genome of each type of RNA virus with its description of function

(+) strand genome -> serves as mRNA, (-) stand genome -> is the compliment to mRNA, double-stranded genome -> consists of both a (+) and (-) strand

Which is most important for attachment of a virus to a host cell?

Viral specificity for host receptors

The term ___ is used to describe the rupture or bursting of a cell.

Lyse

The number of phage particles released from a host cell is called the ___ size.

Burst

In the lytic cycle of the T4 page, lysozyme degrades a portion of the bacterial ___.

Cell wall

Enveloped viruses can derive their envelope from ___.

Certain host organelles, the host cytoplasmic membrane

The process by which a virus is taken up by a host cell as a result of the host cell's cytoplasmic membrane surrounding the virion to form a vesicle is called ___.

Endocytosis

All non-cellular infection agents are viruses.

False

Enveloped and non-enveloped viruses all mature fully in the cytoplasm of the host cell.

False

Enveloped viruses enter the host cell by endocytosis only, while non-enveloped viruses can enter the host cell by fusion or endocytosis.

False

Lysogens are more susceptible to reinfection by the same type of phage.

False

Which of the following directs the incorporation of phage DNA into a bacterial chromosome?

Integrase

Which of the following about classifying viruses is false?

It is not as important as classifying organisms since they are not living entities.

Some pathogenic bacteria produce toxins that are encoded on prophage DNA, and these are examples of ___ conversion.

Lysogenic

___ is a change in the phenotype of a lysogen as a consequence of the specific prophage it carries.

Lysogenic conversion

Most animal DNA viruses replicate within the host cell's ___.

Nucleus

Match each possible outcome of phage replication with the correct definition.

Productive infection -> new viral particles are produced Latent state -> viral genome remains silent within the cell

At a minimum, all viruses are composed of ___.

Proteins, nucleic acids

The enzyme of RNA viruses that lack proofreading ability and thus makes many mistakes compared to the polymerase of DNA viruses is ___.

Replicase

The replication strategy of viruses can be divided into three general categories: those used by ___.

Reverse transcribing viruses, DNA viruses, RNA viruses

An enzyme that uses an RNA molecule as a template to make a complementary copy of DNA is called ___.

Reverse transcriptase

Which of the following are diseases caused by prions?

Scrapie, Bovien spongiform encephalopathy, Creutzfeldt-Jakob disease

Reassortment of gene segments that encode viral surface proteins that are recognized by the immune system can result in a loss of the immune system's ability to recognize and respond to the virus. This phenomenon is called antigenic ___.

Shift

___ transduction is the result of excision errors made as temperate phages transition from a lysogenic to a lytic cycle.

Specialized

What are the two types of transduction?

Specialized and generalized

Phage DNA and proteins are made during the ___ stage of the T4 lytic cycle.

Synthesis

Which of the following are viral protein components that attach to specific receptors on host cells?

Tail fibers, spikes

Which of the following statements about viruses are true?

The viral capsid is composed of protein, viruses contain RNA or DNA but not both

The study of viruses is important because ___.

There are many medically important viruses that cause disease, viruses can be a vehicle for horizontal gene transfer in bacteria, bacteriophages play a significant ecological role in reducing bacterial populations in nature

Viruses are challenging to study because ___.

They are obligate intracellular parasites, they can only be seen using an electron microscope

Which of the following processes are required for production of virus particles in a host cell?

Transcription of viral genes, replication of viral genome, translation of viral genes

Bacteriophages play a fundamental role in which type of horizontal gene transfer?

Transduction

A ___ is an infectious agent that lacks a capsid and consists only of RNA.

Viroid

Rank the following by size, from smallest to largest, starting with the smallest at the top.

Viruses Bacteria Human cells

List the steps of an animal virus infection cycle in the correct order

1. attachment 2. penetration and uncoating 3. synthesis of viral proteins and replication of the genome 4. assembly 5. release

The term ___ is used to describe programmed cell death, a process some non-enveloped viruses trigger as a mean of release.

Apoptosis

Viruses that infect bacteria are called ___.

Bacteriophages (phages)

Viral genomes can be ___.

Either single-stranded or double-stranded

M13 particles are assembled during a process called ___, which the virus uses to exit the cell.

Extrusion

___ transduction is the result of packaging errors during the assembly stage of phage replication.

Generalized

The molecules that viral spikes attach to on the host cell in order to gain entry are typically ___.

Glycoprotiens

Infection of bacteria by ___ phages always ends with the lysis of the host cell.

Lytic

In enveloped viruses, sandwiched between the nucleocapsid and the envelope is the ___.

Matrix protein

One of the early proteins expressed in the T4 lytic cycle is an enzyme called a ___ that degrades the bacterial DNA.

Nuclease

___ are the causative agents of transmissible spongiform encephalopathies.

Prions

Specialized transduction ___

Produced defective phage particles, transfers phage DNA and adjacent host genes, results from errors in excision of the prophage

RNA viruses have a higher mutation rate than DNA viruses because replicase lacks ___ ability.

Proofreading

To maintain the lysogenic state, a ___ protein prevents expression of the gene required for excision.

Repressor

___ phages have the option of entering the prophage state, while ___ phages always burst the host cell shortly after infection.

Temperate, lytic

What mechanisms do newly assembled viruses use to leave their host cell?

Triggering apoptosis, budding

Bacteriophages are important medically because they can be used to prevent the growth of food-contaminating pathogens.

True

The process by which the viral nucleic acid is released from the protective protein coat is ___.

Uncoating

Regarding animal viruses, which of the following statements are true?

Viruses use their spike to attach to host cell receptors, some viruses require more than one host receptor for attachment, blocking a host receptor with a drug would prevent a virus from infecting that cell

HIV is describes as a ___ because it uses revers transcriptase to make a DNA copy from its RNA genome.

retrovirus

Replicases are ___ polymerases.

RNA-dependant RNA

During the ___ or maturation step in viral multiplication, capsids and genetic material are packaged into virions.

Assembly

The ___ or maturation stage of the T4 phage lytic cycle is marked by the formation of new phage particles inside of the host cell.

Assembly

The binding of a bacteriophage surface protein to a host cell receptor is called ___.

Attachment

Enveloped viruses exit host cells be ___; non-enveloped viruses are released upon ___ of the host cell.

Budding, apoptosis