Ch 5: Viruses and Prions

Be sure to enable [answer with definition] and [multiple choice]

__ infect every type of cell, including bacteria, algae, fungi, protozoa, plants, and animals.

Viruses

Seawater can contain __ viruses per milliliter.

100 million

The term virus is Latin for __.

poison.

Viruses are better described as __ or __ rather than alive or dead.

active, inactive

Viruses are __ that cannot multiply unless they invade a specific host cell and instruct its genetic and metabolic machinery to make and release new viruses.

obligate intracellular parasites

__ are obligate intracellular parasites of bacteria, protozoa, fungi, algae, plants, and animals.

Viruses

Viruses are __ in nature and have had major impact on development of biological life.

ubiquitous

Viruses are ultramicroscopic in size, ranging from __ up to __ (diameter).

20 nm, 1000 nm

Viruses are not __; structure is very compact and economical. They do not independently fulfill the characteristics of life.

cells

Basic structure of virus consists of a __ (capsid) surrounding the __.

protein shell, nucleic acid core.

Nucleic acid of viruses can be __.

either DNA or RNA, but not both.

Molecules on virus surfaces give them __ for attachment to host cell.

high specificity

Viruses __ for most metabolic processes.

lack enzymes

Viruses __ for synthesizing proteins.

lack machinery

Which of the following best describes viruses?

Obligate intracellular parasites

True or False: A specific animal virus has the ability to attach to and enter almost any animal host cell. (T/F?)

False

The __ only need these parts to invade and control a host cell:

• External coating

• Core containing one or more nucleic acid strains of DNA or RNA

• Sometimes one or two enzymes

virus

Which viral component:

__ - protein shell that surrounds that nucleic acid.

Capsid

__ viruses consist only of a nucleocapsid.

Naked

Which viral component:

__ - some have external covering of the nucleocapsid, usually a modified piece of the host’s cell membrane.

Envelope

Which viral component:

__ - can be found on naked or enveloped viruses.

• Project from the nucleocapsid or the envelope

• Allow viruses to “dock” with host cells

Spikes

Which viral component:

__ - a fully formed virus that is able to establish an infection in a host cell.

Virion

Capsid of virus are composed of identical protein subunits called __.

capsomers (capsomeres).

Enveloped viruses take a bit of the __ when they are released from a host cell.

cell membrane

Enveloped viruses can bud from all of the following EXCEPT:

They can bud from ALL of these choices

The sum total of the genetic information carried by an organism is called __.

genome.

DNA viruses have the following characteristics EXCEPT:

All choices are characteristics

RNA viruses have the following characteristics EXCEPT:

All choices are characteristics

__ - sense RNA virus: ready for immediate translation (SARS-CoV-2).

Positive

__ - sense RNA virus: must be converted before translation can occur.

Negative

__ - carry their own enzymes to create DNA out of their RNA genomes.

Retroviruses

Which type of virus:

• Enter the host cell’s nucleus and are replicated and assembled there.

DNA viruses

Which type of virus:

• Replicated and assembled in the cytoplasm.

RNA viruses

__ (CPEs): virus-induced damage to the cell that alters its microscopic appearance.

Cytopathic Effects

Types of Cytopathic Effects (CPEs) include all EXCEPT:

Minimal changes in shape and size

Inclusion bodies are compacted masses of __ or damaged cell organelles in the nucleus and __.

viruses, cytoplasm.

__ is the fusion of multiple host cells into single large cell containing multiple nuclei.

Syncytia

Persistent Infections can last for __ or the remainder of the host’s life. Can remain latent in the cytoplasm or in the DNA.

a few weeks

When viral DNA is incorporated into the DNA of the host, it is called a __.

Ex. measles

provirus.

__ - periodically become activated under the influence of various stimuli.

Chronic latent state

Transformation is the effect of __, or viruses that carry genes that directly cause cancer.

oncogenic

These are functions of Transformed cells EXCEPT for:

All of these are functions

__ is a type of virus that are “bacteria-eating”

Bacteriophage

Bacteriophage mostly contain __, but some RNA types exist as well.

double-stranded DNA

Every bacterial species is parasitized by various specific __.

bacteriophages.

__ - undergo adsorption and penetration. Do not undergo replication or release immediately.

Temperate phages

Viral DNA enters an inactive __ state during which it inserted into bacterial chromosome.

prophage

__ - virus in a lysogenic cell becomes activated and progresses directly into viral replication and into the lytic cycle.

Induction

The __ is when a bacterium acquires a new trait from its temperate phage.

lysogenic conversion

__: laboratory-bred animals and embryonic bird tissues.

in vivo

__: cell or tissue culture methods.

in vitro

__ eggs containing embryos:

• intact and self-supporting unit

• sterile environment

• contain their own nourishment

Bird

__ are areas where virus-infected cells have been destroyed and show up a clear, well-defined patches in the cell sheet.

Plaques

Which of the following is not an in vivo method of culturing animal viruses?

All of the choices are in vivo methods.

Creutzfeldt-Jakob disease and Bovine spongiform encephalopathy are caused by prions. Which of the following best describes a prion?

Infectious protein

What have connection to chronic infections?

Ex. Type 1 diabetes, MS, various cancers, Alzheimer’s, obesity

Viruses

Antibiotics designed to treat bacterial infections have __ on viruses.

no effect

True or False: Antibiotics are an effective method for treating viral infections. (T/F?)

False