VIRAL PROPERTIES Flashcards
what is a virion?
the complete, infective form of a virus outside a host cell, with a core of RNA and a capsid.
what’s an icosahedral virus?
when the capsid is made from 20 flat sides giving a spherical shape
what is a helical virus?
nucleic acid surrounded by a hollow protein cylinder or capsid and possess a helical structure
what is an enveloped virus?
when the capsid is encased in a lipoprotein baggy membrane
what is a complex virus?
when the capsid isn’t helical or isocahedral and it may even possess extra structures such as protein tails
what are the key features of viruses?
they’re acellular, depdend on host cells to replicate/make energy/make proteins, genome DNA or RNA
they are intracellular obligate parasites
what are obligate parasites?
an organism that will not thrive and thereby cannot reproduce outside a host.
what are spikes on viruses?
protein/glycoprotein structures protruding from the surface of the virus particles and are involved in contact with the host cell
what is a DNA virus?
a virus that has DNA as its genetic material and therefore replicates using a DNA dependant DNA polymerase
what are the 2 types of DNA virus?
double stranded DNA (dsDNA) and single stranded DNA (ssDNA)
what is an RNA virus?
a virus that has RNA as its genetic material
what are the 3 types of RNA virus?
double stranded RNA (dsRNA), single stranded + sense RNA (ss+RNA) and single stranded - sense RNA (ss-RNA)
whats the difference between positive and negative sense RNA viruses
positive sense RNA viruses can have their genomes directly used whilst negative sense RNA viruses must be copied first by RNA polymerase to form positive sense RNA (as its complementary to mRNA)
what are retroviruses?
single stranded RNA genomes which use DNA intermediates to replicate
(reverse transcriptase converts viral RNA to DNA which can be integrated into the hosts DNA)
what are the pros of viral envelopes?
better protection from hosts immune system, helps it stay wet to remain infectious
what are the pros of non-enveloped viruses?
they are more stable and spread more easily
what are some examples of retroviruses?
HIV
what are some examples of
+ssRNA viruses?
influenza, measles, mumps and rabies
what are some examples of
-ssRNA viruses?
polio, HepC
what are some examples of
dsRNA viruses?
rotavirus
what are some examples of
DNA viruses?
herpes, Epstein Barr virus
why are viral infections prevalent and problematics?
there are few drugs available, they have high mutagenic rates, there are re-emerging infectious diseases and latent/persisting infections
what is ‘infectious dose’?
the quantity of a pathogen measured in the number of organisms that is necessary to cause infection in a susceptible host
what is ‘burst size’?
how many viruses particles are released per cell
what is a lytic viral infection?
when the cell dies and virus particles are released
what are latent viral infections?
when the virus is present but latent and will later emerge in lytic infection e.g. when immunocompromised
