Test 3 - Ch's 13, 14 Flashcards
Define bacteriophage (phage)
Viruses that infect only bacteria.
Define virion
single virus particle
What is the capsid made of?
protein
Nucleocapsid
the capsid and the nucleic acid together
Capsomeres
protein subunits that make up the capsid
What are the three types of vision shapes? Describe.
1- icosahedral - flat triangles
2- helical - like a bedspring
3- complex - nucleocapsid, tail (aka sheath), and tail fibers
Which type of viruses only have the complex shape?
Phages, NOT animal
Naked vs enveloped
Naked virions do not have an envelope, while enveloped have a double layer of lipid outside of the capsid - similar to a cell membrane; attachment spikes may protrude from the envelope
Four genome types?
ss DNA, ds DNA, ss RNA, & ds RNA (only viruses)
What genes must viruses have to survive?
- genes to make the viral protein coat
- to make copies of the viral genome
- to help them get into and out of the host cells
How can viral families be classified?
Created based on genome types (ds DNA), shape (helical), and the prescence/absence of envelope (naked)
What are some additional ways only animal viruses can be classified?
Based on their routes of transmission to animals
What are some of the routes of transmission for animal viruses?
enteric - fecal-oral route
STD - sexual act
zoonoses- transmitted from animal to human ex rabies
respiratory - aerosol (inhaled droplets)
What state is bacteria considered to be in during a latent infection?
lysogenic state
What are the five stages of infection for lytic viruses?
attachement, genome entry, synthesis (2 steps), assembly, release
What is release by the phage during the “genome entry” stage of the lytic virus cycle?
Lysozyme - an end to help break down peptidoglycan
go back to synthesis of t4 phage lifecycle
pg2
Prophage
when the latent/temperate phages DNA is incorporated into the bact’s DNA
Where does site specific recombination occur in the bact’s genome?
between the terminator and the promoter
What does the enzyme excisase do?
acts as a repressor for the phage DNA when inc. into the bact’s genome
Why is it sometimes beneficial for bacteria to have a prophage?
Able to produce toxins only phages have the instructions for
Lysogenic conversion
when having a prophage changes the phenotype of the host bacterium
