Chapter 13 Flashcards
A) What is the comparative size of a virus? [Figure 13.1]
100 to 1000 fold smaller than cells they infect
B) What is a virion? [Figure 13.2]
nucliec acid surrounded by a protein coat and enzymes
1) What is a capsid and how does it protect the virion?
protien coat that protect from enzymes and toxic chemicals
2) What is a nucleocapsid?
nucleic acid and capsid
C) What makes and enveloped virus unique? [Figure 13.2b]
they have lipid bilayer around capsid and between them a speciall matrix protien- makes them more susceptable to disinfectants
1) Why are naked viruses considered “naked”?
ones without an envelope
D) What type of nucleic acid do viruses have?
either rna or dna, but never both
E) How do viruses attach to host cells? [Figure 13.1, 13.2 and Entry of Virus into Host Cell Video]
attatch to receptors on host cell some have protien structures that are called spikes that stick out of their capsid
F) What different shapes do viruses have? [Figure 13.3]
icosahederal- like a ball
helical- cyndrical
complex- what is in most pictures
G) Know the classifications of human viruses. [Table 13.1]
q?????????
H) Know the informal terms for viruses grouped by primary route of transmission. [Table 13.2]
enteric- fecal- oral route(norovirus, roraviruses aka diahrea, enteroviruses)
Respiratory- respiratory or salivary route(influenza measles, rhinoviruses aka colds)
Zoonotic- vector( lice ect) (westnile, dengue)
Sexually- sexual contact (genital herpes
I) What are arboviruses and how did they get their name?
spread by anthropods( west nile, elephantitis) ar (anthropod) bo(born)
A) What are the major types of relationships between viruses and host cells? [Figure 13.4]
It can be a latent phase
or
Productive infection which multiplication can occur leading to the cell lysing, or virons are release by cell so it doesn’t lyse
B) What are lytic or virulent phages?
phages exit via lysing the host.
1) What are so called productive infections?
viral infections/ phages new virus particles are released from cell lysing
2) What is the infection cycle of the T4 phage? [Figure 13.5 and steps in replication of T4 phage in E.coli video]
t4 is protien cell on the phage and it attaches to the receptor of host cell. Then it degrades a small portion of a bacteria.the tail contracts and then injects phage dna into the host . proteins replicate and are made in a sequential order.
1at protiens produced- nuclease degraders, and a protien that modifies the host cell’s rna polymerase - so no host cells genes are expressed.
then phages are formed.
lysozyme is produced which digests the cell’s wall causing it to lyse releaseing phage particles which go and infect other cells.
C) What are temperate phages? [Figure 13.6]
can either become lytic or store their dna into the host cell’s genome
1)What is a lysogenic infection?
is when they store their dna in the host cells gnome.
2) What is a lysogen?
infected cell of lysogenic carriers
D) What do we know about the lambda phage? [Lambda phage replication cycle video]
it is a temperat phage with a linear chromosome, but with ends that connect to eachother forming a circle.
in lysogeny it uses integrase ( enzyme) to insert phage dna into host’s. It can be taken out by another enzyme and then it becomes lytic
1) What is a prophage?
replicates along with host chromosome prior to division
2) What happens during phage induction?
phage escapes damaged host. due to host cells sos system cutting out the respressor protien responsible for the integration of the prophage
E) What is superinfection conversion?
infection by the same phage
F) How are lysogens protected from infections by the same phage?
called immunity to superinfection. This is because the repressor that maintians the prophage will also bind to operators on oncoming dna. the oeratoe is a regualtory region that controls infection , thus it will prevent expression of the dna that joins to ir.
G) What is lysogenic conversion? [Table 13.3]
is a change in the lysogens phenotype du to specific prophage.
H) What are filamentous phages?
single stranded dna tha look like long fibers. They do not kill host cell, but infected cells multiply slower than if uninfected.
1) What do we know about the M13 phage? [Figures 13.7 and 13.8]
it attatched to f pillus on ecoli It hen enter the cell and then it uses cells dna polymerase to make copy of other strand so it can form a double helix which then makes mrna. As this is happening the chage coat protiens make the capsids that form around the phage dna that is excreted.
A)What is generalized transduction?
This is when there is an error in phage assembly. sometimes phages degrade the hosts chromosomes into pieces which are then accidently packaged. These cannot replicate
1)How are generalized transducing particles different from phage particles?
they contain pieces to the dna particles of host instead of phage and cannot replicate.
B) What is specialized transduction? [Figure 13.9]
excision mistake made by the temerate phage during transition from lysogenic to lytic cycle. This is when it accidently excises some of the bacterias dna with the phage, and a peice of phage is left with the bacterias dna. This makes the phages defective, but can go to other host cells and incorperate into it.
A) How do bacteria like Staphylococcus aureus prevent phage attachment?
they produce protiens to cover their receptors on the cell surface so phage cannot attatch.
B) What do restriction-modification systems do? [Figure 13.10]
They have two types of enzymes, restriction and modification.
These are trained to recognize foreign dna and will cut them up.
modification: they protect host from the restiction enzyme by covering it’s dna with methyl groups which makes the dna invisible to the restriction enzymes.
