Chapter 17 - Viruses

Flashcards defining key vocabulary related to viruses as discussed in Chapter 17 of Biol 1115-003.

Virus

A small infectious particle that is not a cell and cannot reproduce without a host cell.

contains capsids and sometimes membranous envelopes with glycoproteins

Capsid

The protein coat that encloses viral nucleic acid.

Capsomere

The protein subunits that make up the capsid.

viral reproduction cycle

1. genome enters through tail apparatus of endocytosis

2. replicating genetic materials

3. uses host resources to make it’s own proteins

4. viral nucleic acids and capsomeres self-assemble into new viruses

5. exits from host cell (damage or destroy)

Bacteriophage

A type of virus that infects bacteria.

Lytic Cycle

A viral reproductive cycle that results in the death of the host cell, producing new phages and lysing the host cell.

Lysogenic Cycle

A viral reproductive cycle where the viral DNA is incorporated into the host cell's chromosome.

every time host divides, it copies phage DNA

temperate phages

phages that use lytic and lysogenic cycles

Retrovirus

A type of virus that uses reverse transcriptase to convert RNA into DNA.

HIV

Human immunodeficiency virus, a retrovirus that causes AIDS.

enveloped, contains 2 RNA, 2 reverse transcriptase

Viral disease in plants

have RNA genome

transferred by

• horizontal transmission: through damaged cell walls

• vertical transmission: inheriting viruses from parent cells

spreads through plasmodesmata

no cure

Viroid

A smaller, less complex infectious agent that causes disease in plants.

Prion

Infectious, misfolded, proteins that cause degenerative brain diseases in mammals.

Prions characters

incubate for years

hard to identify source (mostly source)

commonly in brain

incorrect folded proteins form aggregates that interfere with normal cell functions

Emerging Viruses

Newly discovered viruses that are increasing in communities or have the potential to do so.

why do new viruses appear?

mutations of existing viruses

unnoticed from small human populations

spread from animals (75% of new viruses)

Creutzfelt-Jakob disease

A rare and fatal neurodegenerative disorder caused by prions, (dementia, hallucinations, jerky movements/seizures)

dealth in a few months

mad cow disease

A neurodegenerative disease in cattle caused by prions,degeneration of brain and spinal cord, difficulty moving, weight loss

similar disorders in humans, such as variant Creutzfeldt-Jakob disease.

scrapie

A neurodegenerative disease affecting sheep and goats, caused by prions

scrape wool off, lip smacking, convulsive collapse, death.