Ch 13: Viruses, Viroids, & Prions

bacteriophage

a virus that only infects bacteria

mycophage

a virus that only infects fungi

size of viruses

5 nm to 300 nm

virion

a complete infectious viral particle

helical virus

nucleic acid surrounded by a hollow protein cylinder

polyhedral virus

nucleic acid surrounded by many-sided shell

enveloped viruses

nucleic acid surrounded by either a helical or polyhedral core and covered by an envelope

binal (complex) viruses

Neither helical nor polyhedral forms, are pleomorphic (irregular shaped)

family names

end in -viridae

genus name

end in -virus

PFU (plaque forming units)

Measure of # of viruses that are capable of lysing host cells and forming a plaque

primary cell line

from tissue slices

diploid cell line

from human embryonic tissue

continuous cell line

semi-transformed

lytic bacteriophage

lyse the host bacteria cells as a normal part of their cycle

lysogenic (Temperate phages)

either lytic or incorporate DNA into host cell (prophage)

prophage

incorporation of phage DNA into bacterium genome

phage conversion

host cell has new properties

specialized transduction

virus TAKES some of the host cell DNA, changes properties of the bacteria

spontaneous induction

“self-restarting” the lytic cycle

early stage of viral replication

viral genome is replicated

late stage of viral replication

viral structural proteins and enzymes are replicated

[BLANK] of animal viruses are produced from a single infected host cell

10,000 to 50,000

Positive strand RNA virus

directly translated by host cell’s ribosome into viral proteins

Negative strand RNA virus

transcribed into positive-strand RNA by viral enzyme, then translated into viral proteins by the host’s ribosome

retroviruses

transcribed into dsDNA by reverse transcriptase (viral enzyme)

provirus

a viral genome that has been integrated into the DNA of a host cell

DNA viruses

have both + and - strands, transcribed into viral mRNA by host enzymes first

latent infections

an infection that does not immediately produce detectable symptoms

acute infections

short duration with rapid recovery

persistent (chronic) virus infections

viruses are continually present in the body and can be detected, the disease may or may not be present

proto-oncogene

promotes proliferation (rapid reproduction of cells)

supressor genes

stops growth

sarcoma

cancer of connective tissue

adenocarcinomas

cancers of glandular epithelial tissue

viroids

short pieces of naked RNA

virusoids

viroids enclosed in a protein coat

prions

infectious protein particles - inherited/transmissible by ingestion, transplant, and surgical instruments

PrP^C

normal cellular prion glycoprotein on cell surface

PrP^Sc

scrapie protein, accumulates in brain cells forming plaques