Micro ch 5 CC and Hw

Enveloped viruses leave cell by

budding through host membrane

In vitro

cell or tissue culture of viruses

Viral lysozyme digests the host cell wall, releasing the newly made phage, and lysing the host cell in the release step.

true

Rather than developing more antiviral medications, what is a more common focus for researchers when it comes to viral disease?

vaccine development

Virus

"poison" found in every cell type and habitat

Gram staining of the patient's samples would help to identify which type of pathogens?

Bacteria

How does lysogeny affect humans?

Bacteria can become virulent due to phage genes, causing greater damage to infected human host.

Prions

Composed primarily of misfolded (aberrant) protein (no nucleic acid)

Order these steps of the lytic cycle. A. Assembly B. Penetration C. Lysis D. Synthesis E. Adsorption

E, B, D, A, C

Viroids

Virus-like agents that parasitize plants. About one-tenth the size of an average virus

Choose the statement that correctly explains why viruses are described as "filterable."

Viruses are able to pass through a filter because of their small size.

Why do antiviral medications often have side effects?

Viruses are intracellular pathogens, and therefore, there is often host cell damage with antiviral treatments

Viral spikes

attach specifically to host cell receptors

Of all infectious agents, which group has the most variety of drugs designed to treat infections?

bacteria

Enveloped viruses are usually released from the host cell by

budding

Nonenveloped viruses leave cell by

by cell lysis

Antibiotics would be effective against which of these infections? Check all that apply.

whooping cough, cholera, syphillis,

Antiviral drugs

Almost all antiviral drugs licensed so far have been designed to target one of the steps in the viral life cycle: Integrase inhibitor class of HIV drugs interrupts the ability of HIV genetic information to incorporate into the host cell DNA. Easier to develop vaccines to prevent viral diseases

The T-even bacteriophages such as T2 and T4 infect

E. coli

DNA viruses

Single-stranded (ss) or double-stranded (ds; linear or circular); Enter the host cell's nucleus and are replicated and assembled there

How are temperate phages replicated?

The phage is replicated along with the host cell's genome.

Select the three choices that are the primary purposes of cultivating viruses.

To isolate viruses from clinical specimens, To prepare viruses for vaccines, To research the biology of viruses

Viruses are acellular

True

Select the three methods that are used to cultivate viruses.

Use of cell culture techniques, Use of animal inoculation, Inoculation of embryonated eggs

Provirus

Viral DNA incorporated into the DNA of the host

Persistent infections

cell harbors the virus and is not immediately lysed: Can last from a few weeks to the remainder of the host's life Can remain latent in the cytoplasm

A naked virus fuses with the host cell membrane.

false

All viruses leave a cell by exocytosis.

false

Animal viruses always kill cells they infect.

false

In the lysogenic stage of phage replication, the host cell is lysed.

false

Once a phage becomes lysogenic, it will remain lysogenic and never be lytic again.

false

True or false: Viruses belong to the Domain Archaea

false

Viral nucleic acid is made inside the bacterium and is combined with viral protein coat already present outside.

false

Viruses can be grown on culture media like bacteria.

false

Helical capsid

have rod shaped capsomeres that bond together to form a series of hollow discs resembling a bracelet

Direct fusion

in this form of penetration, the envelope merges directly with the membrane

The activation of a prophage to enter the lytic cycle is called

induction

In vivo

lab bred animals and embryonic bird tissues are used to culture viruses

The viral capsid is

only around the nucleic acid and composed of proteins

In phage replication, _______.

only the phage nucleic acid enters the bacterial cell

Select the infectious agents that are noncellular.

satellite viruses, prions, viroids

Bacteriophage

"bacteria eating": Most contain double-stranded DNA, but some RNA types exist as well. Every bacterial species is parasitized by various specific bacteriophages. The bacteria they infect are often more pathogenic for humans

The correct order of the stages for phage replication are 1 = assembly 2 = attachment 3 = transcription/replication 4 = release 5 = penetration

2, 5, 3, 1, 4

Prophage

A lysogenized bacteriophage; a phage that is latently incorporated into the host chromosome instead of undergoing viral replication and lysis.

Which drug targets can be found on both bacterial cells and viral particles?

None of the choices are possessed by viruses.

The capsid of a virus is

a protein shell that surrounds the nucleic acid

The general steps in viral replication (in order) are

adsorption, penetration, synthesis, assembly, release

Endocytosis

an entire virus is engulfed by the cell and enclosed in a vacuole or vesicle

Retroviruses

carry their own enzymes to create DNA out of their RNA

Latency

cell harbors the virus and is not immediately lysed: Can last from a few weeks to the remainder of the host's life

Inclusion bodies

compacted masses of viruses or damaged cell organelles in the nucleus and cytoplasm

Loeffler and Frosch

discovered animal virus in cattle

Beijernick

discovered tobacco mosaic virus in plants

Every virus particle contains

either DNA or RNA

Viruses are viewed with

electron microscope

Syncytia

fusion of multiple damaged host cells into single large cells containing multiple nuclei (giant cells)

The polio vaccine currently used in the United States, the Salk vaccine, consists of polioviruses that have been treated with chemicals so that they can no longer reproduce within host cells and thus cannot establish an infection. They are referred to as _______, rather than dead, viruses.

inactive

Viruses are usually _________ in size, and their structure is best viewed through the use of ________ microscopy

nanometers; electron

Complex capsid

only found in the viruses which infect bacteria, they can take many shapes, and are never enveloped

A major difference in the replication of animal viruses and bacteriophages is the ______ step.

penetration

A viral infection in which the virus can remain latent in the host cell for weeks to years is described as a(n) _________ infection, and may lead to cancer if host DNA is altered.

persistent

An infection in animals similar to a lysogeny in bacteria is called a(n) ______ infection.

persistent

Viral capsids are composed of

protein

In the attachment step of phage replication, _______.

protein fibers in the phage tail attach to specific receptors on the bacterial cell wall

When present, what is the viral envelope composed of?

proteins and lipids

An envelope is acquired during which step of the viral life cycle?

release

In general, viruses are ________ than bacterial or protozoan pathogens and are most often measured in units called ________.

smaller; nanometers

In viral entry by endocytosis

the host cell's plasma membrane surrounds the whole virion and forms a vesicle

What will happen once a virus has entered a host cell and uncoated?

the synthesis of new virions will occur

Icosahedral Capsid

these capsids form an icosahedron, a 3d, 20 sided figure with 12 evenly spaced corners

A portion of the viral envelope comes from the cell membrane of the host cell.

true

Almost immediately upon entry, the viral nucleic acid alters the genetic expression of the host cell.

true

Both enveloped and naked viruses can enter a cell by endocytosis.

true

Both lytic and lysogenic cycles eventually lead to bacterial host cell damage.

true

RNA viruses

can be double-stranded, but more often single-stranded: can be positive sense or negative sense; Replicated and assembled in the cytoplasm