Viruses and Prions Study Guide Flashcards

A comprehensive set of vocabulary flashcards covering the characteristics, classification, replication, and pathologies of viruses and prions based on Chapter 6 study guides.

Obligate intracellular parasites

A classification for viruses meaning they lack their own metabolism and must infect a host cell to use its machinery for reproduction.

Capsid

The protein shell or coat that surrounds and protects a virus's genetic material and gives the virus its shape.

Capsomeres

Repeating protein units that make up the viral capsid.

Envelope

An outer lipid membrane found in some viruses that surrounds the capsid and helps the virus enter host cells or avoid the immune system.

Spikes (Peplomers)

Protein projections, often made of glycoproteins, sticking out from the capsid or envelope that help the virus attach to specific host cells.

Segmented genome

A viral genome that is broken into several distinct pieces rather than being one continuous piece.

Positive-sense ssRNA virus (ssRNA+)

A virus whose RNA genome already acts like mRNA and can be immediately translated into protein by the host cell.

Negative-sense ssRNA virus (ssRNA-)

A virus whose RNA is the opposite of mRNA and must first produce a complementary mRNA strand before translation can occur.

Retrovirus

A virus that uses reverse transcriptase to convert its RNA genome into DNA before using that DNA to make mRNA; one example is HIV.

Attenuated strains

Weakened versions of a virus caused by mutations, often used in the production of vaccines.

Reassortment

A process occurring when two different viral strains infect the same cell and exchange genetic material to create a new strain.

Antigenic Drift

Small, gradual genetic changes in a virus caused by mutations over time, such as small mutations in influenza's HA and NA spikes.

Antigenic Shift

Large, sudden genetic changes caused by reassortment that can create completely new viral strains and lead to pandemics.

Helical

A spiral-shaped symmetry classification for viral capsids.

Icosahedral

A viral capsid shape characterized by having $20$ sides.

Host range

The specific collection of species that a virus is capable of infecting.

Tropism

The specific type of tissue or cell within a host that a virus is able to infect.

Prophage

Phage DNA that has integrated into the host bacterial chromosome during the lysogenic cycle.

Phage conversion

A phenomenon where a bacteriophage carries genes for pathogenicity factors, such as toxins, into a bacterial host, giving the bacteria new harmful traits.

Uncoating

The step in animal virus replication where the viral genome is released from the protein capsid.

Budding

The process by which enveloped viruses exit a host cell, taking a portion of the host's lipid membrane with them.

Lysis

The process where a host cell bursts or ruptures to release new virions, typically used by naked viruses or bacteriophages.

Latent Infections

A type of persistent infection where the virus remains dormant with little to no replication, causing periodic flare-ups upon reactivation.

Chronic infections

Persistent infections where the virus is continuously present and replicates at low levels over a long period.

Oncogenic virus (oncovirus)

A virus that can cause cancer by disrupting the normal regulation of the host cell cycle, leading to uncontrolled cell division.

Plaque Assay

A laboratory method used to measure viral titer by counting clear spots where infected cells have been destroyed.

Plaque-forming units (PFUs)

The units used to estimate the number of infectious virions in a sample based on a plaque assay.

Agglutination Assays

Tests that detect viruses through antigen-antibody binding, resulting in the clumping or agglutination of particles.

ELISA (Enzyme-Linked Immunosorbent Assay)

A sensitive diagnostic tool that uses antigen-antibody binding and a color change reaction to detect viral antigens or antibodies.

Nucleoside analog ribavirin

An antiviral drug that is incorporated into the viral genome to cause mutations and instability, preventing successful replication.

Prions

Infectious, misfolded proteins that do not contain DNA or RNA and cause normal brain proteins to misfold.

Transmissible spongiform encephalopathies (TSEs)

A group of diseases caused by prions that result in a sponge-like appearance of the brain due to damage.

Iatrogenic CJD

A form of Creutzfeldt-Jakob disease transmitted through medical procedures involving contaminated instruments, transplants, or medical products.