micro test 4 Flashcards
the attachment of the virion to the host cell
adsorption
injection of DNA/RNA into the cell
penetration
uses the cell’s machinery, transcription and translation of viral proteins
synthesis of nucleic acid and protein
capsids self assemble
assembly and packaging
enzymes lyse host cell
release/lysis
what kind of growth curve do viruses have
one step
specificity of viruses for particular hosts is mediated by —
receptors in the host cell surface
what is the eclipse in the one step growth curve
no infectious virions present in the cell (only viruses)
what events occur during the latent period of viral replication
eclipse and maturation
virus DNA may be restricted by host –
endonucleases
host endonucleases only affect what kind of viruses
dsDNA
can viruses modify host DNA
yes
how do restriction enzymes recognize self DNA
methylation of certain bases
what do restriction endonucleases do to DNA recognized as foreign
cleave
– recognize specific sequences of DNA and cleave it
Restriction endonucleases
— modify the DNA at the recognition sequences, preventing endonucleases from actting
methylases
class I virus
dsDNA
class II virus
ssDNA
class III virus
dsRNA
class IV virus
ssRNA, plus sense
class V virus
ssRNA, minus sense
class VI virus
ssRNA, DNA intermediate
class VII virus
dsDNA, ssRNA intermediate
what does plus sense mean
RNA can be read by a translational apparatus in the cell
what does minus sense mean
RNA that is complementary to the translation-able RNA
what do class VI and class VII viruses both use
reverse transcriptase
class I viruses have what type of replication
classical semiconservative
class II viruses have what type of replication
classical semiconservative, discard - strand
class VII viruses have what type of replication
transcription followed by reverse transcription
class III viruses have what type of replication
classical semiconservative of RNA (not DNA)
class IV viruses have what type of replication
make ssRNA (-) and transcribe to make ssRNA (+) genome
class V viruses have what type of replication
make ssRNA (+) and transcribe to make ssRNA (-) genome
class VI viruses have what type of replication
make ssRNA (+) genome by transcription off of - strand of ds DNA, reverse transcription
class III, VII, I, and V viruses both need to – the – strand before becoming mRNA (+)
transcribe, minus
class – viruses can be used directly as mRNA
IV
class – viruses synthesize another strand before transcription into mRNA
II
DNA viruses (3)
I, II, VII
RNA viruses (4)
III, IV, V, VI
why must some types of virus contain enzymes in the virion in order for mRNA to be produced
because they need reverse transcriptase to make an intermediate
class VI viruses are also known as
retroviruses
what is the most common type of bacteriophage genome
dsDNA
what makes T4 bacteriophages resistant to most restriction endonucleases
glucosylation
circular permutation
entire replication of genome plus a little more (13 hours on a clock)
headfuls of cleaved viral genome have the same two starting and ending letters, –
repeated terminal sequences
– phage have alternate life cycles- lytic and lysogenic
temperate
temperate phage life cycle where they can replicate new virions
lytic cycle
temperate phage life cycle where they integrate within the host genome and replicate with the bacterium
lysogenic cycle
a lysogenized cell is called a
prophage
what happens after the lysogenic cycle
lytic cycle
what is the switch from lysogenic to lytic called
induction
the – protein causes repression of the lambda lytic events
cl (lambda repressor)
the – protein controls activation of lytic events
Cro
– destroys the cl lambda repressor resulting in Cro activation
RecA protease
what events need to happen for lambda to become a prophage
adsorption, penetration, injection of DNA, DNA cos sites connect to form a circular molecule, integrase is expressed
many animal viruses are —
enveloped
orthomyxovirus example
influenza
retrovirus example
HIV
herpesvirus example
varicella zoster (chicken pox)
hepadnavirus example
hep B
rhabdovirus example
rabies
animal virus infection where provirus is made or the virus can replicate autonomously outside of the genome of the host, tend not to kill the host; primary acute infection, virus harbored in nervous tissue, recurrent infection, recurrence with trauma or stress
latent infection
animal virus infection where the cell is always infected and virus particles are made and shed continuously, tend not to kill the host cell immediately
persistent infection
up regulated genes that push cell cycle forward, broken gas pedal
oncogenes
down regulated genes that don’t stop the cell cycle, broken brakes
tumor suppressor
Hemagglutinin and Neruaminidase are used to identify strains of
influenza
antigenic – - rearrangement of genome segments to produce different viruses
shift
antigenic – - minor antigenic changes due to genetic mutations
drift
small (~250-400 bp) circular ssRNA particles known to infect plants, naked nucleic acid with no protein encoding regions
viroids
extracellular proteins that cause neurological diseases, mis-folding
prions
result from a change in a single base pair and can lead to a single amino acid change in a polypeptide or to no change at all
point mutations
cause a more dramatic change in DNA than point mutations, including frameshift, often result in complete loss of gene function
deletions/insertions
— genomes typically accumulate mutations at a higher rate than – genomes
RNA, DNA
chemical, physical, or biological agents that increase the mutation rate
mutagens
activated as a result of some types of DNA damage and initiates a number of DNA repair processes, both error prone and high fidelity
SOS regulatory system
what test measures mutagenesis
Ames test
uptake of naked DNA directly from the environment, could be from lysed cells
transformation
phage mediated transfer of DNA
transduction
transfer via cell-to-cell contact, pilus mediated, cell sex
conjugation
if a heat killed S strand of strep pneumoniae and a live R strain are both put in a mouse, will the mouse die
yes, live S and R will be found
will a mouse be killed from the heat killed S strand of strep pneumoniae alone
no
will a mouse be killed from the live R strain of strep pneumoniae alone
no
will a mouse be killed from the live S strain of strep pneumoniae alone
yes
what is the difference between generalized transduction and specialized transduction
specialized includes viral integration in the bacterial chromosome
– plasmid allows gene transfer
F
what is an Hfr strain
when the F plasmid is incorporated into the chromosome
do F- cells become F+ after attaching to a Hfr cell
no
which type of horizontal transfer of genetic information between bacteria may involve the use of the lytic phage as a vector
general transduction
which type of horizontal transfer of genetic information between bacteria may involve the use of a temperate phage as a vector
specialized transduction
regions of dyad symmetry, DNA sequences in which regions are repeated and inverted to each other
molecular/genetic palindromes
two of the same subunit bound through a region of the folded peptide that allows interaction.
homodimers
stimulus-response coupling mechanisms to allow organisms to sense and respond to changes in many different environmental conditions
two component regulatory mechanism
regulation in response to fluctuations in cell population density
quorum sensing
specific sequence of DNA where a particular repressor protein can bind
operator
a – can bind to a sterically hindered repressor to make it the correct shape
corepressor
the – operon is an example of an operon when a repressor needs to bind to a corepressor to prevent amino acid synthesis
arginine
beta-galactosidase breaks down —
lactose
the lac operon is in the default – position
off
a – can bind to an operator bound repressor to prevent it from binding
inducer
the – operon is an example of a operon where a repressor is bound to an inducer and allows for a gene to be expressed
lac
a – can bind to an activator binding site so an unattracted RNA pol can bind to an operon
activator protein
activator proteins must bind to a – to bind to an activator binding site
inducer
– and – are proteins that bind to DNA sites
activators and repressors
– and – are small molecules that interact with repressors or activators to change their activity
corepressors, inducers
the upstream end of the transcription unit is called the
promoter
the downstream end of the transcription unit is called the
terminator
RNA nucleotides are added to the – end of the growing RNA strand made by RNA pol
3’
when the – is transcribed, it will cause an instability in the transcription complex that makes RNA pol fall off
terminator
can multiple prokaryotic genes be controlled by 1 promoter
yes
can multiple eukaryotic genes be controlled by 1 promoter
no
all genes controlled by the same promoter are part of the same –
operon
in Rho – transcription, the terminators encoded in the DNA make a stem loop structure in RNA followed by a UUU residue
independent
the – protein acts at specific sites only, binds to a single stranded RNA, migrates to the paused transcription complex using ATP, and terminates transcription
rho
– have multiple forms of RNA pol
eukaryotes
– have one form of RNA pol
prokaryotes
– means one promoter for multiple genes
polycistronic
where does transcription happen in prokaryotes
cytoplasm
assemblages of bacterial cells attached to a surface via an adhesive polysaccharide matrix
biofilm
dental plaque is a –
biofilm
rhizobium does what
nitrogen fixation
nitrogenase is oxygen sensitive so rhizobia have to
keep O2 levels low
these organisms are consistently found in association with humans and may have various symbiotic relationships with their host
normal flora
these organisms are almost always associated with disease in infected humans, some are obligate parasites
obligate pathogens
these organisms, though normally not pathogens, may cause disease in a compromised host
opportunistic pathogens
is infection always disease
no
– is established microbial growth in the host (vs. host damage)
infection
– is host damage or dysfunction (vs. established growth)
disease
do microbes typically grow in host blood, lymph, organs, or nervous system
no
what is the typical normal flora type (gram, etc)
Gram positive, coagulase negative
S. epi is all over the outside of the body. is it coagulase + or -
negative
the – is a dry and acidic environment on the human body
skin
in newborn mouths, – predominate
aerotolerant anaerobes
in adult mouths, – predominate in gingival crevices
anaerobes
ears mostly have coagulase — staph like s. epi
negative
eyes have mostly coagulase – staph
negative
– helps the eyes keep populations down
tearing
environment in the GI tract with possible high O2 and low pH
stomach
environment in the GI tract with no O2 and high pH
large intestine/colon
does diet have an effect on gut flora
yes
resident flora in the URT are kept in check by —
competition and host defenses
the LRT has — bacteria
few
– helps to keep organisms out of the bladder
urine
does estrogen affect microorgansims in the vagina
yes
what microoranisms predominate in the vagina during estrogen producing years
lactobacilli
pathogenesis that obstructs host function, even if there is not damage to host cells
colonization
pathogenesis where the host is effected regardless of the presence of a viable bacterial cell
toxins
pathogenesis where colonizing cells grow next to host cells that are then damaged when the immune system activates
immune-mediated damage
the preference of an organism toward a particular type of tissue
tissue tropism
the likelihood of a bacteria to cause a disease
virulence
loss of virulence, cell is still alive
attenuation
toxins that are excreted proteins
exotoxins
toxins that are lipopolysaccharides
endotoxins
enterotoxins cause
diarrhea (cholera)
diptheria toxin inhibits
protein synthesis
botulinum toxin inhibits
muscle contraction (acetocholine)
tetanus toxin inhibits
muscle relaxation
— overstimulate the immune system
superantigens
are endotoxins or exotoxins more potent
exotoxins
only – cells have endotoxins
gram negative
diptheria toxin, cholera toxin, tetanus toxin, botulinum toxin, anthrax toxin, and pertussis toxin are all –
A-B toxins
cholera toxin causes an excess of –, which leads to water loss
solutes
botulinum toxin blocks the release of
acetylcholine
“infant” botulism is a –
bacterial infection
tetanus toxin blocks the release of
GABA
general, non-specific mechanisms common to healthy individuals
constitutive defenses
these mechanisms are induced (activated) by exposure to a pathogen, and involve immune system mediated defenses
inducible
food stability is due to several factors, but a major one is –
water availability
yeast produce – and – when they ferment sugar
ethanol and CO2
why are mushrooms considered microorganisms
the mycelium that are growing underground produce it as a fruit
illness from the consumption of food containing microbial toxins, viable organisms might not be present
food poisoning
all food poisoning microorganisms are gram —
positive
an illness from consumption of foods containing pathogenic microorganisms
foodborne infection
