MicroBio Chapter 13: Viruses, Viroids, and Prions

True or False: Viroids contain a capsid but lack an envelope.

False Recall: They do not have a capsid or outer envelope

When two different strains of a segmented virus enter the same cell, reassortment of the gene segments can occur, resulting in ____.

antigenic shift

Through the process of phage ____, a prophage is excised and enters the lytic cycle.

induction

A viral infection in which the viral genome is intergraded into an animal host cell chromosome, yet can reactivate to cause a productive infection, is categorized as a(n) ____ infectious.

latent

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

lysogenic

Transmissible spongiform encephalopathies are caused by ____.

prions

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

repressor

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 recognized and respond to the virus. This phenomenon is called antigenic ____.

shift

A ____ phage can either cause lytic infection or can incorporate DNA into the host genome as a prophage.

temperate

Which are the two major categories of viral infections?

-Acute -Persistent

Which cytopathic effect is a distinct region representing the site of viral replication? -Tumor -Inclusion body -Giant cell -Syncytium

-Inclusion body

Which of the following directs the incorporation of phage DNA into a bacterial chromosome? -Gyrase -Isomerase -Integrase -Polymerase -Lysozyme

-Integrase

Match each possible outcome of phage replication with the correct definition. -Productive infection -Latent state =New viral particles are produced =Viral genome remains silent within the call

-Productive infection= New viral particles are produced -Latent state= Viral genome remains silent within the call

Which of the following are cytopathic effects of viruses? -Syncytia -Inclusion bodies -Elementary bodies -Reticulocytes -Encapsulation

-Syncytia -Inclusion bodies

What mechanism do newly assembled viruses use to leave their host cell? -Triggering endocytosis -Triggering apoptosis -Fusion -Budding

-Triggering apoptosis -Budding

A prion is best described as ____. -an obligate aerobe -an obligate intercellular parasite -an RNA-based infectious agent -a proteinaceous infectious agent

-a proteinaceous infectious agent

When cultivated in flasks, human cells from solid tissues ____. -grown in suspension -adhere to the bottom surface (substrate) -grown as a monolayer -form multi-layered, tumor-like masses

-adhere to the bottom surface (substrate) -grown as a monolayer

True or False: All non-cellular infectious agents are viruses.

False

True or False: Lysogens are more susceptible to reinfection by the same type of phage.

False

True or False: Most bacteria engulf bacteriophages as a part of the phage replication strategy.

False

True or False: When a bacterial culture is infected with a temperate phage, all particles of the phage will lysogenic their host.

False

____ is a change in the phenotye of a lysogen as a consequence of the specific prophage it carries.

Lysogenic Conversion

One of the system of a respiratory virus infectious is coughing and sneezing. This allows. -viral particles to be shed from the host and transmitted to a new host - even more viral particles from environment to access the host respiratory tract

-viral particles to be shed from the host and transmitted to a new host

Viruses that infect bacteria are called ____.

-phages -bacteriophages

The physical rupture of a cell is termed ____.

Lysis

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

Specialized

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

Transduction

Phage heads that contain only bacterial DNA are called generalized ____ particles.

transducing

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

virulent

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

burst

Although live animals and fertilized chicken egg have been used to cultivate animal viruses in the past these have now been largely replaced by ____ culture.

cell

In a lysogenized bacterium, ____ of the prophage results in a lytic infection.

excision

Animal viruses _____. -can be grown in bacterial cell cultures -can only be grown in animal cells

-can only be grown in animal cells

Symptoms of acute viral diseases result from ____. -viral budding -host tissue damage -lysogenic conversion -host immune response

-host tissue damage -host immune response

All of the following are common features of primary cell lines EXCEPT _____. -protein synthesis -limitless growth -DNA replication

-limitless growth

Protection of lysogens from infection by the same phage is called ____.

immunity to superinfection

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

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

Attachment

In ____ transduction, only bacterial gene adjacent to the prophage can be transferred; whereas In ____ transduction, any bacterial gene can be transferred.

Blank 1: Specialized Blank 2: Generalized