Chapter 5: Viruses and Prions

A single virus particle could contain a genome consisting of ______.

RNA only or DNA only

Viruses CANNOT ______.

Synthesize proteins and replicate outside of a cell

Lysogeny

The condition in which the bacterial host chromosome carries bacteriophage DNA

Release

The final step in the multiplication cycle of viruses in which the assembled virus particle exits the host cell and moves on to infect another cell.

Host range

The limited range of host cells that each type of virus can infect and parasitize.

Uncoating

The process of removal of the viral coat and release of the viral genome by its newly invaded host cell.

Induction

The process whereby a bacteriophage in the prophage state is activated, begins replication, and enters the lytic cycle.

Endocytosis

The process whereby solid and liquid materials are taken into the cell through membrane invagination and engulfment into a vesicle.

Capsid

The protein covering of a virus's nucleic acid core

Assembly (viral)

The step in viral multiplication in which capsids and genetic material are packaged into virions.

viruses represent the smallest infectious agents

True

Which facts best support the position that viruses are not living organisms?

Viruses do not have any means of independent metabolism and cannot reproduce on their own

Lysogeny is best described as ______.

integration of the viral genome into the host chromosome

Most RNA viruses will assemble the virion within the host cell's _______.

cytoplasm

Budding is the release of ______ viruses.

enveloped

A virus with a rod-shaped capsomer has a(n) ________ capsid, while a virus with a capsid arranged as a multifaceted polygon has a(n) _________ capsid.

helical; icosahedron

Since the hepatitis B virus can only infect liver cells in humans and not in other animals, its _________ is considered to be highly restrictive.

host range

Viruses which have symmetrical 20-sided capsids are called ____.

icosahedron

A bacterium acquires a new trait from its temperate phage through a process called _________.

lysogenic conversion

Most DNA viruses will assemble their virions within the host cell's _______.

nucleus

Some animal viruses are called ______ because they enter a host cell and permanently alter its genetic material, leading to cancer.

oncogenic

At minimum, all viruses are composed of ______.

proteins and nucleic acids

The process of a virus losing its capsid (and envelope, if it has one) and exposing viral nucleic acids to the immediate environment.

uncoating

Adsorption

A process of adhering one molecule onto the surface of another molecule.

General phases in the life cycle of animal viruses

Adsorption Penetration Uncoating Synthesis Assembly Release

Prophage

Bacteriophage DNA that is embedded in the bacterial host's DNA

Which is closest in physical proximity to the nucleic acid of a virus?

Capsid

Capsomers

Capsids exhibit symmetry due to the regular arrangement of these subunits. Are monomers of capsid

Identify all the methods that a virus can use to gain entry into an animal cell.

Engulfment/phagocytosis of the virus and fusion of the viral envelope and the cell membrane

The viral envelope and capsid are the same thing.

False

Prion

A group smaller and simpler than viruses that can cause serious disease than humans and animals. The diseases are progressive and universally fatal. Each have the deposition of distinct protein (without nucleic acid) fibrils in the brain tissue.

Icosahedron

A regular geometric figure having 20 surfaces that meet to form 12 corners. Some virions have capsids that resemble icosahedral crystals

bacteriophages (phages)

A virus that infects bacteria

Mature virus particles are constructed from nucleic acid and protein during the ______ phase of the viral life cycle. In viral multiplication, capsids and genetic material are packaged into virus particles during this step.

Assembly

Inclusion body

Is a mass of viruses or damaged organelles caused by viral infection of a cell

Syncytia (singular: syncytium)

Is the fusion of multiple damaged host cells into single large cells containing multiple nuclei

Synthesis (viral)

The step in viral multiplication in which viral genetic material and proteins are made through replication and transcription/translation.

Penetration (viral)

The step in viral multiplication in which virus enters the host cell.

Bacteriophages can increase the pathogenicity of their bacterial host.

True

Viruses are a unique group of biological entities known to infect every type of cellular, such as bacteria, algae, fungi, protozoa, plants, and animals.

True

The 2 principal processes by which viruses penetrate host cells are _________ (engulfment) and direct fusion.

endocytosis

Viruses have a compact and economical structure that is ______.

not cellular

During the lysogenic cycle, viral DNA enters an inactive ______ state, during which it is inserted into the bacterial chromosome. It is used to describe the phage DNA that is latently incorporated into the bacterial host genome.

prophage

All viruses have two parts: a ______ covering and ______ located in a central core.

protein; DNA or RNA

Chronic latent state

It remains hidden within body cells but periodically becomes reactivated.

Envelope

Many animal viruses also possess an additional covering external to the capsid

Persistent infections

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

Provirus

When viral DNA is incorporated into the DNA of the host

Enveloped viruses are released from host cells through ______ (exocytosis), while naked viruses are released through ______ (rupture).

budding; lysis

At minimum, viruses are composed of nucleic acid and a ________ comprised of protein

capsid/shell

The uncoating step in a viral life cycle, where the genome is released from the capsid, is not required in a bacteriophage because ______.

the phage genome is directly injected into the cell cytoplasm

Which type of phage generally can increase the pathogenicity of a bacterium?

temperate phage

Which step in the life cycle of an animal virus is not needed in the life cycle of a bacteriophage?

uncoating