Viruses Flashcards
T/F: viruses infect all living organisms.
: we carry viral genomes as part of out own genetic material
both T
virus’ were discovered as
an agent that causes tobacco mosaic disease, it could pass through a .2 micro meter filter that retained bacteria
virus sizes range from
20-700 nm
giant viruses like pandoraviruses and mimiviruses
are hosted by amoebas, are dsDNA viruses, have a large genome >1Mbp >1000 genes, and are up to 1 micrometer
what are viruses
are infectious obligate intracellular parasites, they can propagate only by host cells, all viruses make mRNA that is translated by the host cell ribosomes
T/F
- viruses regulate transport of materials into and out of themselves
- perform any metabolic reaction
- they replicate autonomously
- F
- F
- F
T/F
- viruses contain nucleic acid based genome
- they transfer their genome from one host cell to another
- they cange over time according to selective pressure
- T
- T
- T
a T4 phage only has what cycle
lytic cycle
temperature phages like lambda phage have what cycle
both the lytic and the lysogenic
give 3 traits of animal viruses
~the genome is a type of nucleic acid (DNA/RNA)
~protein capsid
~some of them posses an envelope
are viral genomes large
no all viral genomes at small and simple containing few genes
the proteins encoded by viral genome are
~protein needed for replicating the genome
~proteins needed for packaging and delivery
~proteins that modify structure and function of host cell
the protein shell is made of
one or more subunits (capsomers) arranged in regular arrays
the capsid has what shape
helical or icosahedral
functions of the capsid are
protect the viral genome during transfer between host , deliver the viral genome, recognize and package newly formed nucleic acid genomes
give 4 traits of the virus’ envelope
~ external membrane layer (not in all viruses)
~ lipid bilayer from host cell (budding)
~ protein of the envelope are instead encoded by the viral genome
~ its function is the attachment of the virus to the host cell
non enveloped virus’ protection comes from
the proteins
give 4 traits of naked viruses
~ are more environmentally stable and resistant to drying and detergents
~ are resistant to gastric and biliary acids
~ cause host cell lysis when released
~ ex: adenovirus, rhinovirus, rotavirus
give 4 traits of enveloped viruses
~ are unstable in environment, and easily inactivated by detergents, acids and heat
~ cannot survive in the GI tract
~ exit from host cell by budding
~ ex: influenza virus, HIV
which survives longer on hands : enveloped or naked virus
naked
how are viruses transmitted
direct contact, aerosols, insect bites, contaminants in food/water, sexual transmission, blood and blood contaminated material
the infectious cycle
~ attachment and entry with release of viral genome
~ genome replication and synthesis of viral proteins
~ assembly
~ release
viral tropism
the type of receptor a virus binds to determines which type of cells and organism will be affected.
some viruses need more than on receptor
primary receptor CD4m co-receptor chemokine. for HIV
HIV causes
AIDS
retroviruses
are enveloped RNA viruses, like rous sarcoma virus and HIV, during infection the viral RNA id converted to dsDNA by the viral protein reverse transcriptase
list the 4 steps of the infectious cycle of a retrovirus
~ virus enters the cell by membrane diffusion
~ reverse transcriptase make dsDNA
~ the DNA provirus is integrated permanently into the hosts’ genome by viral integrase
~ when proviral DNA is activated new virions are produced
what is the effect of lytic infections on cells
host are killed by virus release
what is the effect of chronic/persistent infections on cells
cells may remain infected for a long time and produce viruses at low levels Hepatitis B
what is the effect of latent infections on cells
the viral genome is kept within cells in a quiescient state but can occasionally activate. cold sores and chicken pox
what is the effect of Transforming infections on cells
infected cells exhibit altered growth properties that might trigger oncogenesis
