Microbiology Chapter 13

Which of the following viruses can be latent? (a. HIV)(b. chickenpox virus)(c. herpesviruses)(d. all of the above)

(d. all of the above)

Retroviruses are a type of ________.

+ssRNA

What are the four types of RNA viruses?

+ssRNA, retroviruses, -ssRNA, and dsRNA

4th stage of lytic replication

Assembly of new virions within the host cell

1st stage of lytic replication

Attachement of the virion to the host cell

Which form of PrP is characterized by alpha helices?

Cellular PrP

________ eggs are a useful medium for viruses because they are inexpensive, are among the largest of cells, are free of contaminating microbes, and contain a nourishing yolk.

Chicken

Genome of a virus may be _____or _______.

DNA or RNA

Most _____ viruses assemble in and are released from the nucleus into the cytosol, whereas most ______ viruses develop solely in the cytoplasm.

DNA, RNA

A process by which the viral capsid attaches and sinks into the cytoplasmic membrane, creating a pore through which the genome alone enters the cell.

Direct penetration

Who first demonstrated that viruses are acellular with an experiment designed to elucidate the cause of tobacco mosaic disease?

Dmitri Ivanowski

Process by which attachment of the virus to receptor molecules on the cell's surface stimulates the cell to endocytize the entire virus.

Endocytosis

2nd stage of lytic replication

Entry of the virion or its genome into the host cell

All mammals make a cytoplasmic membrane protein called ________.

PrP

____________ PrP acts enzymatically to convert cellular PrP into prion PrP by inducing a conformational change in the shape of cellular PrP.

Prion

Which form of PrP is characterized by beta-pleated sheets?

Prion PrP

Which form of PrP is disease-causing?

Prion PrP

What is the name of the enzyme that is carried by -ssRNA?

RNA-dependent RNA transcriptase

5th stage of lytic replication

Relese of the new virions from the host cell

Who discovered prions?

Stanley Prusiner

3rd stage of lytic replication

Synthesis of new nucleic acids and viral proteins by the host cell's enzymes and ribosome

_________ against some viruses can also be prepared in egg cultures.

Vaccines

infectious, pathogenic RNA particles that lack capsids but do not infect plants--- affect some fungi.

Viroidlike agents

___________ are extremely small, circular pieces of RNA that are infectious and pathogenic in plants.

Viroids

Tobacco mosaic virus was isolated and characterized by who?

Wendell Stanley

Replication of _______ takes more time than replication of _______.

animal viruses, bacteriophages

8 steps, in order of lysogeny

attachment, entry, prophage in chromosome, replication and cell division of chromosome & virus, induction, synthesis, assembly, release

What are the 5 steps of lytic replication?

attachment, entry, synthesis, assembly, release

a virus that infects bacterium

bacteriophage

virus that infects bacteria

bacteriophage

tumors that remain in place and are not generally harmful

benign

harmless neoplastic cells

benign tumor

PrP plas a role in the normal activity of the ______.

brain

Enveloped animal viruses are often released via a process called ________.

budding

invasive neoplastic cells

cancer

Once a virus is inside, the _____ is removed

capsid

protein coat of virus

capsid

protein coat surrounding a nucleic acid core

capsid

proteinaceous subunits that make up the capsid of a virus

capsomeres

consists of cells isolated from an organism and grown on the surface of a medium or broth; also called tissue cultures

cell culture

What are the 2 forms of PrP?

cellular PrP and prion PrP

capsid of a ________ virus have many different shapes that do not fit readily into the other two categories

complex

: derived from tumor cells; divide relentlessly providing a never-ending supply of new cells

continuous cell cultures

Replication of a virus usually results in what for the host cell?

death or lysis

created from embryonic animal, plant, or human cells that have been isolated and provided appropriate growth conditions; die after 100 cell divisions

diploid cell cultures

What are the 2 types of cell cultures?

diploid cell cultures and continuous cell cultures

3 different mechanisms of animal viruses

direct penetration, membrane fusion, and endocytosis

Viroids (do, do not) have capsids.

do not

Viruses (do, do not) have function organelles?

do not

The genomes of most _______ viruses enter the nucleus of the cell, where cellular enzymes replicate the viral DNA in the same way they would replicate the host DNA.

dsDNA

What are the 4 classifications of RNA and DNA?

dsDNA, ssDNA, ssRNA, dsRNA

a membrane on the outside of a virus

envelope

phospholipid membrane that surrounds the nucleocapsid in some virons

envelope

A virus with a membrane is a(n) __________ viron.

enveloped

Viruses are dependent on their hosts' ________ and __________ to produce new virons.

enzymes, organelles

So far, _________ have been established for all viral genera, but only three viral _________ are described

families, orders

All known prion disease involve __________, _________, and __________.

fatal neurological degeneration, the deposition of fibrils in the brain, and the loss of brain matter such that eventually large vacuoles form

capsid of a _______ virus is composed of capsomeres that bond together in a spiral fashion to form a tube around the nucleic acid

helical

What are the 3 basic viral shapes?

helical, polyhedral, and complex

Fungal viruses exist only (inside, outside) cells.

inside

Modified replication cycle in which infected host cells grow and reproduce normally for many generations before they lyse.

lysogeny

A virus without a membrane is a(n)___________ viron.

naked

phenomenon of uncontrolled cell division in a multicellular animal

neoplasia

Viruses are classified by their type of __________, presence of ________, ________, and _________.

nucleic acid, presence of an envelope, shape, and size

What is the genetic material of a virus?

nucleic acids

Together, the nucleic acid and the capsid are called a __________.

nucleocapsid

What is the active form of a protooncogene called?

oncogene

When a provirus is incorporated into its host DNA, the condition is ________.

permanent

infections with enveloped viruses in which host cells shed viruses slowly and relatively steadily

persistent infections

A virus that is specific for a bacterial host is called a _________.

phage

After incubation an agar plate includes a uniform bacterial lawn interrupted by clear zones called _______.

plaques

Example of an +ssRNA virus

poliovirus

capsid of a _________ virus is roughly spherical, with a shape similar to a geodesic dome

polyhedral

single stranded viral RNA that can act directly as mRNA.

positive strand RNA (+RNA)

a proteinaceous infectious agent that was different from any other known infectious agent in that it lacked nucleic acid

prion

What is an inactive bacteriophage called?

prophage

inactive virus within bacterial cell

prophage

_________ play a role in cell division and are also believed to play a role in cancer development.

protooncogenes

dormant virus in a eukaryotic cell

provirus

Diseases caused by -ssRNA viruses include ________ and _________.

rabies, flu

transcribes DNA from RNA

retrovirus

The genome of hepatitis B viruses is replicated using an RNA intermediary instead of replicating DNA fro ma DNA template. This process is mediated by a viral enzyme ________.

reverse transcriptase

Which of the following is not an acellular agent? (a. viroid)(b. virus)(c. rickettsia)(d. prion)

rickettsia

Parvovirus is the same as _________.

ssDNA

when it enters the nucleus of a host cell, the enzymes produce a new strand of DNA complementary to the viral genome.

ssDNA

Animal viruses typically lack ________, having ________ instead.

tails, glycoprotein spikes

What are the phages in lysogeny called?

temperate phages or lysogenic phages

Another name for a complete virus is ________. (a. virion)(b. viroid)(c. prion)(d. capsid)

virion

complete viral particle

virion

extracellular state of a virus outside of the cell

viron

A ________is a minuscule, acellular, infectious agent having one or several pieces of nucleic acid-- either DNA or RNA.

virus

The smallest viruses are _____ nm in diameter whereas the largest are approx _____ nm in diameter

10, 400

Process by which the viral envelope and the host cell membrane fuse, releasing the capsid into the cell's cytoplasm and leving the envelope glycoproteins as part of the cell membrane.

Membrane fusion

__________ or _________ do not deactivate prions, though they are destroyed by incineration or autoclaving in 1 normal NaOH.

Normal cooking, sterilization procedures

The process whereby a prophage is excised from the host chromosome is called _________.

induction

Common effect of dsRNA virus

infant diarrhea

Lysogenic phages can change the phenotype of a bacterium, for example from a harmless form into a pathogen. This is a process called _______.

lysogenic conversion

Some animal viruses may remain dormant in cells in a process known as ______.

latency

The viruses involved in latency are called _________ or __________.

latent viruses or proviruses

Plaques are areas where phages have ___________.

lysed the bacteria

mass of neoplastic cells

tumor

The removal of a viral capsid within a host cell is called ________.

uncoating

removal of capsomeres from a virion

uncoating