Viruses 2 Flashcards
importance of viruses of prokaryotes
they can be used to kill bacteria - bacteriophages
genome of viruses of prokaryotes
majority are double stranded
how do we detect viruses
biochemical (enzymatic assays and PCR and NA hybridization), serological (IF, IP, IB, ELISA, RIA), electron microscopy
do you detect viruses and virions the same way
no
how do you estimate how well virion are doing
if it makes 1% of what it is supposed to make - quantity over quality
what are plaque assays based on
based on CPEs (growth lacking where they grow)
used in bacterial cells to demonstrate viable phage numbers, used to detect total virions in mammalian cells, viral particles must be viable
point here is that it is only used to detect virions which are viable viruses
how are viruses used as tools?
• Molecular and cellular biology
– Manipulate systems to investigate function of cells
• Genetics
– Have contributed to understanding of DNA replication, transcription, translation, transport
• Gene therapy
• Immunology
– Understanding our immune system
do viruses have protein synthesis machinery and division by binary fission
no – they use host’s machinery system
where does protein synthesis for virus occur
in the cytoplasm of the host cell
what are virioids and where are they usually found
infectious, subviral particles
found in plant diseases
type of genome in viroids
small circular single stranded DNA
do viroids encode protein
no but they replicate autonomously
what are pseudovirons
they contain non viral DNA but are infectious and do not replicate
what are defective virus/satellites
they are viral kind of viruses that cannot encode capsid protein so they depend on helper viruses for their propagation(replicating), ssRNA, and DNA
example of a defective virus
Hep D
what does Hep D (delta agent) use as its helper
Hep B
why is Hep D considered “viroid-like”
because it does code for its own protein
are prions viruses
no
properties of prions
proteinaceous and infectious but no NA
where do virophages grow
only in a strain of the mimivirus within the infected amoeba – that can infect us
what is the first virophage discovered and describe it
sputnik: an 18 Kb circular double-stranded DNA, icosahedral virus
what do virus need to do to propagate (to replicate)
– Infect an appropriate host cell
– Use the host cell to generate more of itself
– Get out of the host cell to do it all over again
what are the phases of viral life cycle
- Eclipse phase - infectious virus cannot be seen or recovered from infected cells
- Maturation (there is a lot of it)
- Latent phase - progeny virus accumulates intracellularly but it hasn’t been released yet - ends when free virus is released
when does latent period end
when it becomes extracellular aka when the free virus is released
