Virology Flashcards

Flashcards on Virology

Virus

A very small infectious, obligate intracellular parasite that needs a host cell to carry out genome replication and synthesis of virus component parts. Progeny virions formed in host cells are the means of transmission of the virus to the next host cell.

Virion

The infectious form of a virus.

Virus Properties

Viruses use host cells to carry out processes for replication to produce new virions and spread to new hosts, utilizing host resources like nucleotides, amino acids, ribosomes, ATP, and Golgi apparatus.

Virus Classification

Viruses are classified by nucleic acid type (DNA or RNA, single or double stranded), capsid symmetry (helical, icosahedral, complex), presence or absence of an envelope, and genome characteristics.

Virus Components

A virus contains nucleic acid (DNA or RNA), a protein coat (capsid) surrounding the nucleic acid, and sometimes an envelope or capsule.

Capsid

The protein coat surrounding the nucleic acid of a virus, composed of capsomers.

Capsomers

Protein subunits that make up the capsid of a virus.

Nucleocapsid

The combination of the viral nucleic acid and capsid.

Bacteriophages

Viruses that infect and replicate within bacteria, characterized by complex structures and classified by shape and nucleic acid.

Bacteriophage Structure

Composed of a head, collar, tail, tail pins, and tail fibers.

Bacteriophage Life Cycle

A 5-step life cycle: attachment, penetration/entry (injection), synthesis of nucleic acid and protein, assembly and packaging, and release (lysis).

Attachment (Virus)

Attachment proteins on the outside of the virus attach to specific receptors on the host cell surface.

Lytic Cycle

Infected bacteria are used as a production factory for bacteriophages and are lysed to release new bacteriophages.

Lysogenic Cycle

The bacteriophage genome is incorporated into the bacterial host chromosome by genetic recombination.

Prophage

The name for bacteriophage DNA when it is inserted in the bacterial host chromosome.

Tobacco Mosaic Virus

An example of a plant virus with helical symmetry and 2130 identical capsomers.

Virus Entry (Plants)

Plant viruses enter through cell walls and membranes

Non-enveloped viruses

Example: Polio virus, such as picornaviruses, exhibits icosahedral capsids containing >60 capsid proteins.

Enveloped viruses

Envelope derived from cell, golgi or nuclear membrane. Enveloped viruses have to bud or burst from cell. Examples: measles virus, influenza virus.

Virus Glycoproteins

Inserted in the membrane, form spikes on the outside of the virus, and are the main antigens for the immune system. Matrix protein links virus nucleocapsid to the membrane

Enveloped Virus Life Cycle

Involves fusion with the cell membrane, synthesis of nucleic acid and viral proteins, assembly at various sites, and budding from the cell to release progeny viruses.

Retrovirus

An RNA virus that converts its genome into double-stranded DNA using reverse transcriptase, integrates into the host DNA, and can undergo latency or produce new virus particles.

Reverse Transcriptase

An enzyme used by retroviruses to convert RNA into DNA.

Virus Culture

Viruses are obligate intracellular parasites that can be grown in cell culture to observe cytopathic effects; eggs are also sometimes used (influenza virus).

Primary Cell Culture

Obtained from live animal tissue with a limited life span.

Continuous Cell Lines

Immortal cell lines, usually from cancerous cells, that do not stop growing.

Cytopathic Effect

The effect of a virus on cells under a microscope, including transformation (tumor formation), lysis (cell death), persistent infection, and latent infection.

Plaque Assay

A method for quantifying viruses by inoculating them on a monolayer of cells or bacteria, resulting in holes or plaques of dead cells. Can also be used to isolate single viruses