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.
C)What does the CRISPR system do? [Figure 13.11]
this is when a cell survives phage infection and saves peices of phage dna in chromosome in the CRISPR region. this is so it can recognize and protect itself from subsequent infections of same phage.
1)What does CRISPR stand for?
Clusters of Regularly Iinterspersed Short Palindromic Repeats.
A) What are plaque assays used for?
used to know how many phage particles.
1) What exactly are plaques? [Figure 13.12]
circular zones which show cell lysis caused by phage dna
2) What is the titer?
phage concentration in the original plate suspension
A)What do animal viruses have on their surface?
studded with attatchment protiens or spikes which are bound to glycoprotiens in the plasma membrane
B) What must HIV do before it can enter a cell?
must bind to two receptors
C) What makes some animals resistant to certain diseases?
the diseases cannot connect to the two receptors required.
D) How do enveloped viruses enter a cell? [Figure 13.3]
2 different mechanisms:
fusion with host membrane:
endocytosis:
E) How do naked viruses enter a cell?
can only enter via endocytosis read 318
F) What is the process of uncoating and which type of viruses do it?
in all viruses: The phage nucliec acid must be speparated from capsid. this process is called uncoating. this is done by virus scpecific mechanisms which release viral genome.
H) What two things need to happen for production of viral particles in an infected cell to take place?
- expression of viral genes to produce protiens to make capsid and enzymes required for replication.
- synthesis of multiple copies of genome.
I) How do DNA viruses replicate? [Figure 13.4a]
typically replicate in the nucleus using host cells machinery to perform replication
J) How do RNA viruses replicate? [Figure 13.4b]
replicate in cytoplams. requires replicase
1) What is replicase?
a virally encoded rna polymerase
2) What is antigenic drift?
the rna polymerase has no proof reading and can make mistakes, this forms mutations. This can make a different antigen. ex: influenza changes from year to year.
K) How do reverse-transcribing viruses replicate? [Figure 13.4c]
rna is used as template to make dna
1) What is a Retrovirus? What are some examples?
?
human imunodeficeincy. HIV. It’s rna in smplanted into the cell and is used as a template to make 1 strand dna. then it’s compliment is made and is integrated into host cells dna. Hep B.
L) Where does the assembly process take place for animal viruses?
in cytoplasm or nucleus
M) What is budding? [Figure 13.5 and Mechanism for releasing enveloped virions video]
when cell goes to release virus. This si when protine spikes of virus insert into host cells membrane nuceloplasmids are excised and are covered in the matrix built up in those areas.
N) How do naked viruses leave a host cell?
released when the host cell dies. they initiate apoptosis( cell programed death)
A) What are acute infections? [Figure 13.16a]
Infections that can infect a host, but then be eliminated
B) What are persistent infections? [Figure 13.16b-c and Table 13.4]
Infections where the infection cannot be eliminated. There are 2 types chronic, and latent
1) What are chronic infections? What are some examples?
Chronic infections are those like HPV ect which will stay active and persistent till the host dies
2) What are latent infections? What are some examples?
Latent infections are those which will go into a inactive state in which the host doesn’t expirence symptoms, but then it will activate and the symptoms will arise in the host.
- What is a provirus? [Figure 13.17
This is an inactive virus. when the virus doen’t integrate into the cell’s chromosomes, but is independent like a plasmid. They can replicate on their own when they want.
A) What is a tumor?
where hosts cells are mutated causing the cell to grow and reproduce abnormally.
B) What are proto-oncogenes?
They are genes in cells that regulate growth
C) What is a oncogene? How can viruses with them lead to tumors? [Table 13.5]
They are genes carried via virus that are similair to proto oncogenes, and mess with the growth causing tumors.
D) Review Figure 13.18
q
A) What was the only way to study animal viruses back in the day?
they would innoculate animals with the virus, or they would innoculate a fertilized chicken egg
B) How can you use cell and tissue culture to study animal viruses?
you provide a medium that they can grow in although it is really slow.
1) What is a primary culture? [Figure 13.9]
when you isolate one cell in a meduim and let it replicte
2) What is the cytopathic effect? [Figure 13.20]
when you can tell what virus it is by the morphologicall change that occurs to the cell.
3) What is an inclusion body?
when infected cells congregate at site of viral replication
C) How can a plaque assay be used to find animal virus concentration?
you look at the clear zones
D) How can you use an electron microscope to count animal viruses? [Figure 13.21]
if it is high enough concentration.
E) What is a quantal assay and how is it used?
this is when they innoculate a number of subject and then you see which were killed and it is given as a percentage
1) What is the ID50?
infective dose 50%
2) What is the LD50?
Lethal Dose 50%
F) What is hemagglutination? [Figure 13.22]
when viruses connect to multiple rbc s this causes ten to agregate.
A) How can you recognize of viral infection in a plant? [Figure13.23]
stunted growth, tumours, yellowing, etc
B) What is an example of a plant that has been maintained in a virus-infected state? [Figure 13.24]
tulips
C) How do viruses infect plants?
they are carirind through bug or humans going from plant to plant
A) What are viroids? [Figure 13.25]
onlly carries short sta rna hat in in a circle.
B) What are prions? [Table 13.6, Figure 13.26 and Prion diseases video]
Prions are protiens that in brain kill neurons
1) What does the term transmissible spongiform encephalopaties mean?
Term for all prions disease .. arose from the spongy like texture of brains infected by prions.
2) What are PrPc and PrPsc? [Figure 13.27]
prPc - is normal non infectious prions
Prpsc- prion prtotien scrapies- infectious
3) How do prions cause disease?
a
4) What are some examples of prion diseases?
mad cows diseasen jacobs disease
