BIOL 2041 - Ch. 13 Viruses, Viroids, and Prions

Viruses have DNA or RNA?

either, but not both

Viruses have no

ribosomes or ATP-generating mechanism

receptor sites for animal viruses

typically on plasma membrane

virion

fully developed viral particle

capsid

virus protein coat made of capsomeres

envelope

lipid, protein, and carbohydrate coating on some viruses

helical virus

hollow, cylindrical capsid; rabies and ebola

polyhedral virus

many sides; poliovirus

complex virus

complicated structure; bacteriophage

virus family name ends in

viridae

virus order name ends in

ales

virus genus name ends in

virus

baltimore classification system

based on virus nucleic acid and how mRNA is produced

bacteriophage plaque

clearings on a lawn of bacteria on surface of agar, each plaque corresponds to a single virus

PFU

plaque forming unit

lytic cycle

phage cause lysis and death of host cell

lysogenic cycle

phage DNA incorporated into host DNA, remains dormant as a prophage

steps of lytic cycle

attachment, penetration, biosynthesis, maturation, release

prophage

inserted phage DNA

animal virus steps

attachment, entry, uncoating, biosynthesis, maturation, release by budding

uncoating

separating the viral nucleic acid from its capsid by viral or host enzymes

how are enveloped viruses released from host cell

budding

how are non-enveloped viruses released from host cell

rupture

DNA virus biosynthesis

replicate DNA in host cell nucleus, synthesize capsid proteins in cytoplasm, capsid proteins migrate to nucleus for assembly

DNA virus examples

Adenoviridae, Poxviridae, Herpesviridae, Papoviridae, Hepadnaviridae

Coronaviridae

single stranded RNA, enveloped

Togaviridae

single stranded RNA, enveloped

Picornaviridae

single stranded RNA, non

Rhabdoviridae

single stranded RNA, mostly enveloped

Adenoviridae

double stranded DNA, non

Poxviridae

double stranded DNA, enveloped

Herpesviridae

double stranded DNA, enveloped

Papovaviridae

double stranded DNA, non

Hepadnaviridae

double stranded DNA, enveloped

Retroviridae

single stranded RNA, produce DNA intermediate

Reovirus

double stranded RNA, non

Rotavirus

double stranded RNA, non

reverse transcriptase

produces DNA from viral RNA genome

latent virus

remains in asymptomatic host cell for long period; Herpesvirus, Shingles

Persistent viral infection

occurs gradually over a long period and is generally fatal; papillomavirus, Hepatitis B

prions

scrapie protein accumulates in brain cells and forms plaques, misfolds other proteins and spreads

prion disease examples

mad cow disease