BIO 246 Chapter 13: Viruses, Viroids, and Prions

Complete set of 58 vocabulary flashcards covering viruses, bacteriophages, animal virus replication, oncogenic viruses, cytopathic effects, cultivation, diagnostics, and prions for BIO 246 Microbiology Exam 3.

Viruses

Non-living infectious agents that reproduce only inside living host cells.

Obligate intracellular parasites (viral)

Organisms or agents that require living host-cell machinery to make viral proteins and reproduce.

Viral genome

A viral genetic core containing either DNA or RNA, never both.

Universal viral structures

The two components found in all viruses: nucleic acid (DNA or RNA) and a protein capsid.

Capsid

The protein coat that surrounds and protects the viral genome.

Capsomeres

Protein subunits that make up the capsid.

Variable viral structures

Structures found only in some viruses, including an envelope, surface spikes, and replication-related enzymes.

Viral envelope

A lipid-containing outer covering acquired as a virus leaves a host cell.

Viral spikes

Structures that bind to specific receptors on host cells and help the virus attach.

Naked virus

A virus without an envelope; attachment structures may be located on its capsid.

Host range determinants

Compatible host-cell receptors and cellular factors needed for viral growth.

Tissue tropism

The particular cells or tissues in a host that support a virus's growth.

Viral classification criteria

Characteristics commonly used to classify viruses, including nucleic-acid type, replication strategy, and morphology.

-viridae

The suffix used for virus family names.

-virus

The suffix used for virus genus names.

Bacteriophage

A virus that infects bacteria.

Lytic cycle steps (bacteriophage)

The five steps in order: attachment, penetration, biosynthesis, maturation, and release.

Phage attachment

The step in which the phage binds to specific receptors on the bacterial surface.

Phage penetration

The step in which the phage injects its nucleic acid while its capsid usually stays outside.

Viral biosynthesis

The step in which the viral genome directs the host to make viral nucleic acid and proteins.

Viral maturation

The step in which viral components assemble into complete virions.

Phage release (lytic cycle)

The step in which the bacterial cell lyses, releasing newly assembled phages.

Lytic cycle

A replication cycle where a phage replicates and assembles new viruses, then lyses and kills its host.

Lysogenic cycle

A cycle in which phage DNA integrates into the bacterial chromosome and is copied as the cell divides.

Prophage

Bacteriophage DNA integrated into a bacterial chromosome.

Prophage induction / lytic entry

The process by which an integrated prophage leaves the bacterial chromosome to begin producing new phages via the lytic cycle.

Animal-virus replication steps

The six steps of animal-virus replication: attachment, penetration, uncoating, biosynthesis, maturation, and release.

Animal virus penetration methods

Entry mechanisms often occurring by receptor-mediated endocytosis or fusion of the viral envelope with the host membrane.

Uncoating

Removal of the viral covering so the genome becomes available inside the host cell.

Budding

The method by which enveloped animal viruses commonly exit cells, acquiring an envelope from host-cell membranes.

Non-enveloped animal virus exit

The release mechanism for non-enveloped animal viruses, which commonly occurs by lysis of the host cell.

Provirus

Viral genetic material that persists in an animal host cell during a latent-like state.

Penetration difference: phages vs. animal viruses

Phages usually inject their genome, whereas animal viruses generally enter as whole particles.

Acute viral infection

A relatively short infection, such as influenza or the common cold.

Persistent viral infection

A long-lasting infection that the immune system does not clear.

Latent viral infection

An infection where viral material remains dormant with few or no symptoms and may later reactivate.

Latent viral infection examples

Herpes/cold sores or varicella-zoster virus, which can reactivate as shingles.

Oncovirus

A virus capable of initiating tumors or cancer.

Human papillomavirus (HPV)

A virus associated with cervical cancer.

Epstein–Barr virus (EBV)

A virus associated with Burkitt lymphoma.

Hepatitis B virus and hepatitis C virus

Viruses associated with liver cancer.

Human herpesvirus 8 (HHV-8)

A virus associated with Kaposi sarcoma.

Human T-cell leukemia virus 1 (HTLV-1)

A virus associated with human T-cell leukemia.

Cytopathic effects (CPE)

Structural changes or damage in host cells caused by viral infection.

Syncytia

Enlarged giant cells formed when infected cells fuse, containing multiple nuclei.

Common cytopathic effects

Cell size/shape changes, inclusion bodies, syncytia, lysis, DNA/chromosome changes, and cancerous transformation.

Plaques

Clear areas where bacteria have been destroyed on a bacterial lawn, used to cultivate bacteriophages in the lab.

Animal virus cultivation hosts

Cell cultures, embryonated eggs, or living animals.

Polymerase chain reaction (PCR)

A laboratory method that can detect or identify viral nucleic acid.

Serological tests

Diagnostic tests that detect antibodies against viruses or detect viral antigens using antibodies.

Prion

An infectious misfolded protein particle that contains no nucleic acid.

Prion resistance

High resistance exhibited by prions to inactivation and usual sterilization methods.

Mechanism of prion damage

The process whereby abnormal prion proteins induce normal proteins to misfold and accumulate.

Spongiform encephalopathy

A disease causing sponge-like cavities in brain tissue and severe neural damage.

Prophage vs. Provirus

A prophage is phage DNA integrated into a bacterial chromosome, whereas a provirus is viral material persisting in an animal host cell.

Lytic vs. Lysogenic cycle

The lytic cycle leads to immediate virus production and host lysis, while the lysogenic cycle maintains viral DNA in the host genome as the cell divides.

Budding vs. Lysis destructiveness

Budding may allow enveloped viruses to exit without immediately killing the host cell, making it less destructive than cell lysis.

Viral growth requirement

Viruses cannot grow on ordinary artificial media alone because they require living cells to supply machinery for viral replication.