Describe the hereditary material in viruses vs living organisms.
viruses: DNA or RNA, single or double stranded
organism: DNA and always double stranded
Describe the plasma membrane in viruses vs living organisms.
viruses: no membrane
organisms: have membrane
Describe transcription in viruses vs living organisms.
viruses: doesn’t occur
organisms: occurs
Can viruses carry out translation independently?
no
All viruses contain…
- genetic material (DNA or RNA)
- capsid
some contain an outer phospholipid membrane called an envelope
Describe the variety of viral genomes.
- linear or circular
- DNA or RNA
- single-stranded (ss) or double-stranded (ds)
- options are dsDNA, ssDNA, dsRNA, or ssRNA
What are the 3 categories of ssRNAs?
- positive sense
- negative sense
- abisense
What is positive sense?
sequence matches the mRNA, so its directly read by the ribosomes to synthesize proteins
What is negative sense?
sequence is complementary to mRNA; must be copied before translation
What is ambisense?
part of genome is pos sense, the other is negative sense
What is the viral growth cycle also referred to as?
lytic cycle because it ends with lysis of bacterial host cell
Describe the 6 phases of the lytic cycle.
- viral genome enters the host bacterial cell
- viral genome transcribed to produce viral proteins (gene expression)
- viral genome replicated
- particles assemble inside host
- particles exit to exterior
- free virions in tissue or environment are transmitted to new host
Viruses enter a cell via _________.
uncoating
What is uncoating?
viral capsid is removed and the genome is released
What are the two mechanisms enveloped viruses follow ?
- viral proteins bind to a receptor causing the viral membrane to fuse with the cell membrane
- virions enter via endocytosis; acidification causes viral proteins to change shape, promoting release
What are the classes of DNA viruses?
- Class I: dsDNA
- Class II: ssDNA
What are the classes of RNA viruses?
- Class III: dsRNA
- Class IV: (+)ssRNA
- Class V: (-)ssRNA
All require RNA replicase
What are the classes of reverse-transcribing viruses?
- Class VI: (+)ssRNA RT
- Class VII: dsRNA RT
require reverse transcriptase
How are viruses classified?
- genome and morphology
- nature of host species
- how the virus replicated within the host
What are antiviral drugs?
designed to target specific viruses at specific stages of infection
What are vaccines?
activate immune response
