Chapter 13: Viruses, Viroids, and Prions

Virus

Acellular infectious particle that must use a living host cell to multiply.

Obligate Intracellular Parasite

An organism or particle that must live inside a host cell to reproduce.

Virion

A complete fully developed viral particle.

Host Cell

A living cell that a virus infects and uses to make more viruses.

Host Range

The types of host cells a virus is able to infect.

Attachment Site

A specific receptor on a host cell that a virus must bind to before infection.

Bacteriophage

A virus that infects bacteria.

Viral Nucleic Acid

The genetic material of a virus which may be DNA or RNA.

Capsid

Protein coat that surrounds and protects viral nucleic acid.

Capsomere

Protein subunit that makes up a viral capsid.

Envelope

Outer lipid protein and carbohydrate covering found on some viruses.

Spikes

Projections on the outside of some viruses that help them attach to host cells.

Helical Virus

Virus with a hollow cylindrical capsid shape.

Polyhedral Virus

Virus with a many-sided capsid shape.

Enveloped Virus

Virus surrounded by an outer envelope.

Complex Virus

Virus with a complicated structure such as a bacteriophage.

Viral Taxonomy

The system used to classify and name viruses.

Virus Genus

A virus naming group that usually ends in virus.

Virus Family

A virus naming group that usually ends in viridae.

Virus Order

A virus naming group that usually ends in ales.

Viral Species

A group of viruses with similar genetic information and the same host niche.

Plaque

A clear area on a bacterial lawn where bacteriophages destroyed bacteria.

Plaque-Forming Unit (PFU)

A measurement used to count infectious virus particles by plaques.

Cell Culture

A method of growing animal viruses in living cells.

Cytopathic Effect (CPE)

Visible damage or deterioration in host cells caused by viral infection.

Serological Test

A test that uses antibodies to identify viruses.

Western Blotting

A test that detects viral proteins using antibodies.

PCR

A test that detects viral nucleic acid.

Viral Multiplication

The process where a virus enters a host cell and uses it to make new viruses.

One-Step Growth Curve

A graph showing viral multiplication inside host cells over time.

Eclipse Period

Stage when complete viruses are not visible because viral parts are being made.

Acute Infection

A rapid infection where virus numbers rise quickly.

Lytic Cycle

A bacteriophage cycle that ends with lysis and death of the host cell.

Lysis

The breaking open of a host cell.

Lytic Attachment

Step where a phage attaches to the bacterial host using tail fibers.

Lytic Penetration

Step where phage DNA enters the bacterial host cell.

Lytic Biosynthesis

Step where the host cell makes phage DNA and proteins.

Lytic Maturation

Step where new phage particles are assembled.

Lytic Release

Step where phage lysozyme breaks the cell wall and new phages exit.

Lysogenic Cycle

A bacteriophage cycle where phage DNA becomes part of host DNA.

Lysogeny

A latent state where phage DNA remains inside the host cell.

Prophage

Phage DNA inserted into bacterial DNA.

Phage Conversion

When a bacterium gains new properties because of a prophage.

Specialized Transduction

Transfer of specific bacterial genes to another bacterium by a phage.

Animal Virus Attachment

Step where an animal virus attaches to the host cell membrane.

Receptor-Mediated Endocytosis

Entry method where a host cell takes in a virus after receptor binding.

Fusion

Entry method where a viral envelope fuses with the host cell membrane.

Uncoating

Removal of the viral capsid to release viral nucleic acid.

Animal Virus Biosynthesis

Production of viral nucleic acid and proteins inside the host cell.

Animal Virus Maturation

Assembly of viral nucleic acid and capsid proteins into new viruses.

Budding

Release method where an enveloped virus exits with part of the host membrane.

Rupture

Release method where the host cell breaks open and releases viruses.

DNA Virus

A virus with DNA as its genetic material.

DNA Virus Replication

Replication that usually occurs in the host cell nucleus.

Adenoviridae

Double-stranded DNA nonenveloped viruses that can cause respiratory infections.

Poxviridae

Double-stranded DNA enveloped viruses that can cause skin lesions and smallpox.

Herpesviridae

Double-stranded DNA enveloped viruses that can cause cold sores chickenpox and other diseases.

HHV-1 and HHV-2

Herpesviruses that cause cold sores.

HHV-3

Herpesvirus that causes chickenpox.

HHV-4

Herpesvirus that causes mononucleosis.

HHV-5

Cytomegalovirus.

HHV-8

Herpesvirus associated with Kaposi’s sarcoma.

Papovaviridae

Double-stranded DNA nonenveloped viruses that can cause warts and cancer-related changes.

RNA Virus

A virus with RNA as its genetic material.

RNA Virus Replication

Replication that usually occurs in the host cell cytoplasm.

RNA-Dependent RNA Polymerase

Enzyme RNA viruses use to make RNA from RNA.

Positive-Sense RNA

Viral RNA that can directly serve as mRNA for protein synthesis.

Negative-Sense RNA

Viral RNA that must be copied into positive-sense RNA before proteins are made.

Double-Stranded RNA

Viral RNA containing both sense and antisense strands.

Picornaviridae

Single-stranded positive RNA nonenveloped viruses including rhinovirus.

Rhinovirus

Virus that causes the common cold.

Rhabdoviridae

Single-stranded negative RNA viruses including rabies virus.

Lyssavirus

Virus genus that includes rabies virus.

Rabies

Viral disease caused by Lyssavirus.

Filoviridae

Enveloped helical RNA viruses including Ebola and Marburg viruses.

Paramyxoviridae

RNA viruses that can cause measles mumps and parainfluenza.

Orthomyxoviridae

RNA viruses with multiple RNA strands including influenza A B and C.

Bunyaviridae

RNA viruses including hantavirus.

Arenaviridae

RNA viruses associated with diseases such as Lassa fever.

Deltaviridae

Satellite RNA virus family associated with hepatitis D.

Retrovirus

RNA virus that makes DNA using reverse transcriptase.

Reverse Transcriptase

Enzyme that makes DNA from an RNA template.

Provirus

Viral DNA integrated into the host chromosome.

Retroviridae

Virus family that includes retroviruses.

Lentivirus

Retrovirus genus that includes HIV.

HIV

A lentivirus that uses reverse transcriptase and can cause AIDS.

Hepadnaviridae

DNA virus family that uses reverse transcriptase.

Hepatitis B Virus

Hepadnavirus that can cause hepatitis and liver tumors.

Oncogenic Virus

A virus that can cause cancer.

Oncogene

A gene that can transform normal cells into cancer cells.

Sarcoma

Cancer of connective tissue.

Adenocarcinoma

Cancer of glandular epithelial tissue.

Epstein-Barr Virus

A herpesvirus linked to some cancers.

Human Papillomavirus (HPV)

Virus that can cause warts and some cancers.

Latent Viral Infection

Infection where a virus remains hidden and may reactivate later.

Cold Sores

Example of a latent viral infection.

Shingles

Example of a latent viral infection caused by reactivation.

Persistent Viral Infection

Viral infection that develops gradually over a long time.

Plant Virus

Virus that infects plants and often enters through wounds or insects.

Viroid

Short piece of naked RNA that infects plants.