Shared Flashcard Set

Details

Microbiology Assessment 2
UTHSC College of Medicine Class of 2014
268
Microbiology
Professional
05/05/2011

Additional Microbiology Flashcards

 


 

Cards

Term
1.     What are Bacterial chromosomes made up of?
Definition
1.     Double stranded DNA
Term
2.     What form are most (50%) or Bacterial chromosomes in?
Definition
2.     Single circular molecule, 1-9 Mb
Term
3.     What other forms do bacterial chromosomes take?
Definition
3.     Single circular molecule, more than one circular molecule, single linear molecule, more than one linear molecule
Term
4.     T/F Extrachromosomal elements are essential for bacterial growth.
Definition
4.     F – not essential for bacterial growth under normal circumstances
Term
5.     What 2 forms of extrachromosomal elements are there in bacteria?
Definition
5.     Plasmids, Bacteriophages
Term
6.     What are some variable chromosomal elements that are present in some strains and not others?
Definition
6.     Integrated Plasmids and bacteriophages, Remnants of plasmids and bacteriophages, transposable elements, Pathogenicity islands
Term
7.     What is a large contiguous block of DNA encoding groups of genes involved in pathogenesis called?
Definition
7.     Pathogenicity Island
Term
8.     What types of things do Pathogenicity Islands encode for?
Definition
8.     Virulence factors – toxins, secretion systems, pili, ect.
Term
9.     How can P. Islands be recognized?
Definition
9.     Often have different G+C content then the rest of the chromosome
Term
10.  How are P. Islands thought to have originated?
Definition
10.  Horizontal gene transfer
Term
11.  What are the 3 types of Recombination?
Definition
11.  Homologous, Site-specific, Transposition
Term
12.  Which type of Recombination is used for lambda integration?
Definition
12.  Site-specific Recombination
Term
13.  Which type is used for generalized transduction, transformation and conjugation?
Definition
13.  Homologous
Term
14.  Which type is used by insertion sequences, transposons, and phage Mu?
Definition
14.  Transpostion
Term
15.  How does Site-specific work?
Definition
15.  Requires very little homology and uses enzymes that recognize apecific sites and recombine them
Term
16.  What type requires host- or phage-encoded homologous recombination proteins?
Definition
16.  Homologous Recombination
Term
17.  What type involves insertion of transposable elements into different hon-homologous sites in the host DNA?
Definition
17.  Transposition
Term
18.  What are the 3 regions of the prokaryotic gene?
Definition
18.  Regulatory Region, Coding Region, Termination Region
Term
19.  What codes for the protein to begin?
Definition
19.  Initiator Codon – ATG
Term
20.  When does the mRNA begin coding?
Definition
20.  Before the ATG codon
Term
21.  Where does the ribosome bind?
Definition
21.  Upstream or ATG
Term
22.  What region has the most base pairs?
Definition
22.  Coding region 300-3000bp
Term
23.  What else is within some genes in the regulatory region?
Definition
23.  Repressor binding sites, activator binding sites
Term
24.  What do most isolated genes have?
Definition
24.  Promoter and terminator
Term
25.  What is a DNA segment that when transcribed produces a single mRNA which encodes for more than one polypeptide called?
Definition
25.  Operon
Term
26.  What is a Gene?
Definition
26.  A segment of DNA encoding a single polypeptide
Term
27.  What is a Regulon? Example?
Definition
27.  Single regulatory protein that affects multiple operons; the arginine biosynthetic regulon
Term
28.  What is it called when multiple genes and operons are controlled by a single stimulus? Example?
Definition
28.  Stimulon; heat shock, cold shock
Term
29.  T/F Transcription and Translation in Prokaryotes is coupled.
Definition
29.  T
Term
30.  How does the direction of transcription correspond to the lengths of the mRNA transcripts?
Definition
30.  The more laden with ribosome the transcript the earlier they were transcribed
Term
31.  How is Transcription and Translation coupled?
Definition
31.  Ribosomes bind in succession to the nascent mRNA molecule and begin translation while the mRNA is being transcribed from the DNA. mRNA degradation follows close behind.
Term
32.  What is the process of Translation of an mRNA?
Definition
32.  Ribosome recognizes a binding site (rbs) around 6-9 bp upstream of initiation codon (AUG), Translation of gene until Stop codon is reached. At the end of the mRNA will be a transcription terminator.
Term
33.  Do prokaryotic genes have introns?
Definition
33.  No – the gene and the polypeptide product are collinear
Term
34.  T/F many bacterial genes are grouped into multicistronic operons.
Definition
34.  T
Term
35.  What does a cistron/gene encode for?
Definition
35.  Single polypeptide
Term
36.  What is the difference in Transcription and Translation between Eukaryotes and Prokaryotes?
Definition
36.  Prokaryotes – coupled, translation begins before the entire mRNA is transcribed; Eukaryotes – the mRNA must leave the nucleus to be translated in cytoplasm
Term
37.  What does the prokaryotic mRNA lack on its 5’ and 3’ ends that eukaryotic mRNA has?
Definition
37.  5’ 7-methyl GTP cap, 3’ poly-A tail
Term
38.  What are prokaryotic proteins initiated with?
Definition
38.  N-formyl methionine
Term
39.  What does N-formylated peptides act as?
Definition
39.  Chemoattractants for neutrophils and monocytes
Term
40.  What are mutations?
Definition
40.  Changes in the DNA sequence, change the genotype, may or may not change the phenotype
Term
41.  What are the 5 types of Mutations?
Definition
41.  I. Base substitution mutation; II. Frameshift mutations; III. Large deletions; IV. Large insertions; V. Large inversions or translocations
Term
42.  What is a transition?
Definition
42.  Purine à Purine (G àA) Pyrimidine àPyrimidine (Cà T)
Term
43.  What is a Transversion?
Definition
43.  Purine to Pyrimidine (G or A à C or T) Pyrimidine to Purine (C or T à G or A)
Term
44.  What is a missense mutation?
Definition
44.  Protein function altered by incorporation of a different amino acid
Term
45.  What is a Nonsense mutation?
Definition
45.  Stop codon generated
Term
46.  What is a mutation called that is an insertion of deletion of one or two bases?
Definition
46.  Frameshift mutations
Term
47.  What would characterize a Large deletion?
Definition
47.  hundreds to thousands of contiguous bases are lost, leading to severely defective or undetectable proteins
Term
48.  What are large insertions caused by?
Definition
48.  insertion of transposable element
Term
49.  If large inversions or translocations are not genetically programmed, what can they cause?
Definition
49.  severe defects in protein function
Term
50.  What are 2 examples of spontaneous mutations?
Definition
50.  1. mistakes made during DNA replication and repair; 2. Mutations caused by natural exposure to mutagens.
Term
51.  What are some examples of Natural Mutagens?
Definition
51.  UV light, cosmic rays, heat, transposable elements
Term
52.  What are some examples of purposeful mutagens?
Definition
52.  X-rays, UV light, chemical mutagens, transposable elements
Term
53.  At what frequency to mutations caused by purposeful exposure to mutagens occur?
Definition
53.  10-3 to 10-5
Term
54.  What DNA repair system is highly error-prone?
Definition
54.  SOS repair system
Term
55.  What is the frequency of mistakes made during DNA replication and repair?
Definition
55.  10-6 to 10-9
Term
56.  What are 3 regulatory Mechanisms?
Definition
56.  1) Change in the DNA sequence; 2) transcriptional regulation; 3) posttranscriptional regulation
Term
57.  What are used in transcriptional regulation?
Definition
57.  Activators and Repressors
Term
58.  What are 3 forms or posttranscriptional regulation?
Definition
58.  Covalent modification, proteolytic cleavage, binding to host cell proteins
Term
59.  What is it called when an effector molecule binds a protein altering its ability to interact with its substrate?
Definition
59.  Allostery
Term
60.  What is a regulatory protein called that turns ON the genes when bound to DNA?
Definition
60.  Activator
Term
61.  What is a repressor?
Definition
61.  regulatory protein that turns genes OFF when bound to DNA
Term
62.  What is a chemical called that when bound to the regulatory protein turns genes ON?
Definition
62.  Inducer
Term
63.  What is a Negative regulation caused by binding of a chemical to the regulatory protein called?
Definition
63.  co-repressor
Term
64.  How are catabolic operons usually regulated?
Definition
64.  positive regulation, (the default state is off)
Term
65.  What type of operons are often negatively regulated?
Definition
65.  Biosynthetic operons (default state is on)
Term
66.  How is regulation by small molecules accomplished?
Definition
66.  by the concentration dependence of binding of the small molecules to the regulatory proteins.
Term
67.  How do bacteria use catabolite repression?
Definition
67.  distinguish between good and poor carbon sources and repress the lac operon gene until all the glucose is used up.
Term
68.  How is catabolite repression mediated?
Definition
68.  concentration of cAMP, inversely related to glucose levels. (Glucose High – cAMP low; Glucose low – cAMP high)
Term
69.  What regulatory protein is involved in catabolite repression?
Definition
69.  Cabolite Activator Protein (CAP) (also called CRP – cAMP receptor protein)
Term
70.  Where does CAP bind and what kind of regulatory protein is it?
Definition
70.  Promoter region of lac operon; activator protein
Term
71.  What does CAP interact with?
Definition
71.  RNA polymerase and turns on transcription
Term
72.  T/F CAP alone can bind to the promoter DNA.
Definition
72.  F – Only CAP in a cAMP-CAP complex can bind to DNA.
Term
73.  What is the monitor of cAMP levels?
Definition
73.  CAP
Term
74.  What is the lac operon transcribed from the promoter as?
Definition
74.  polycistronic mRNA
Term
75.  How does the absence of the inducer prevent lac mRNA transcription?
Definition
75.  Lac repressor binds to operator
Term
76.  What is the inducer of the Lac Operon called?
Definition
76.  allolactose
Term
77.  In the presence of allolactose what happens?
Definition
77.  binds to repressor, causes conformational change that makes the repressor unable to bind to operator DNA
Term
78.  Once the repressor is inactivated why are only a small number of transcripts made?
Definition
78.  lac promoter is poor
Term
79.  What happens in the absence of both glucose and lactose?
Definition
79.  High cAMP levelsàbinds to CAPà cAMP-CAP complex binds to the promoter, BUT no Lactose so no Inducer (allolactos), so repressor stays bound to operator, No Transcription, No lac mRNA
Term
80.  What happens in the presence of Lactose but the absence of glucose?
Definition
80.  Lac repressor binds inducer, cAMP binds CAP, cAMP-CAP complex binds promoter causeing high levels of transcription
Term
81.  What is the Trp Operon?
Definition
81.  encodes the five enzymes needed for biosynthesis of amino acid tryptophan.
Term
82.  What is the leader peptide and where is it located?
Definition
82.  contains 2 tryptophans near its C-terminus; between the operator and the first gene.
Term
83.  What is the default condition of the Trp Operon?
Definition
83.  ON, it’s a biosynthetic operon
Term
84.  What causes the repressor protein to become active and bind the operator?
Definition
84.  excess tryptophan
Term
85.  In High concentrations of Trp how is the leader mRNA translated?
Definition
85.  quickly, preventing the stable 2-3 hairpin, and leading to the formation of the 3-4 hairpin that serves as a terminator.
Term
86.  What occurs at low concentrations of Trp?
Definition
86.  ribosomes stall at the 2 trp codons, allowing the 2-3 hairpin to form an anti-terminator structure, allowing transcription to proceed.
Term
87.  What do hairpin 1-2 and 3-4 cause and why?
Definition
87.  termination; no protein synthesis
Term
88.  What do virulence factors do?
Definition
88.  foster survival and multiplication in the host
Term
89.  What type of signals do Bordetella pertussis us for virulence gene expression?
Definition
89.  temperature, SO4, nicotinic acid
Term
90.  What type of organisms use Iron as a Signal?
Definition
90.  Corynebacterium diphtheria, E. Coli, Pseudomonas aeruginosa
Term
91.  How does the Two-Component Regulatory system work?
Definition
91.  The sensor and transducer are phosphorylated by a signal, the P-Transducer activates transcription
Term
92.  What is Quorum Sensing?
Definition
92.  the ability of the cell to sense the cell density
Term
93.  What do bacterial pathogens use quorum sensing for?
Definition
93.  to co-ordinate their expression of virulence genes in order to evade the immune response
Term
94.  What can be used to interfere with quorum sensing?
Definition
94.  chemical agents
Term
95.  What is quorum sensing especially important in forming?
Definition
95.  Biofilms
Term
96.  What are 3 reasons why Gene Transfer in Bacteria are medically important?
Definition
96.  1) spread of antibiotic resistance; 2) exchange of virulence factors; 3) antigenic variation
Term
97.  T/F Gene transfer is rare.
Definition
97.  T – varies from 10-2 to 10-6 per cell
Term
98.  What is Transformation?
Definition
98.  the transfer of genetic information from one cell to another via naked DNA
Term
99.  What are some examples of bacteria that can naturally transform?
Definition
99.  Gram Negative – Campylobacter spp, Haemophilus influenza, Neisseria meningitides Gram Positive – Bacillus subtilis, Clostridium botulinum, Strep. pneumoniae
Term
100.        What is the ability to bind and take up DNA called?
Definition
100.        competence
Term
101.        How is DNA structured during uptake into the recipient cell in natural transformation?
Definition
101.        fragmented
Term
102.        What 2 forms of artificial Transformation uptake DNA in an intact form?
Definition
102.        Induced and Electroporation
Term
103.        What is an example of Induced transformation?
Definition
103.        high salt and heat shock for E. Coli
Term
104.        What happens in Electroporation?
Definition
104.        cells exposed to short burst of high electric field that transiently permeabilizes the cells and causes them to take up molecules for the surrounding medium
Term
105.        T/F Competence is involved in Electroporation.
Definition
105.        F
Term
106.        What are the steps in the Gram Positive Species Transformation Process?
Definition
106.        1) DNA released from cell; 2) DNA binds to cell surface receptor and taken up into the cell, 1 strand is degraded; 3) single strand invades its homologous region and displaces one original strand; 4) heteroduplex is replicated, producing 1 tranformant and one unaltered recipient genome; 5) Close genetic markers can be transformed together on a single DNA fragment
Term
107.        What are the 2 exceptions in Gram-Negative Transformation?
Definition
107.        1) DNA binding requires specific sequences in the double-stranded DNA in order to bind the receptor. 2) DNA is taken up in a double-stranded form in a membrane vesicle.
Term
108.        What is the membrane vesicle called?
Definition
108.        transformasome
Term
109.        What involves the direct transfer of genetic information form one cell to another via cell to cell contact?
Definition
109.        Conjugation
Term
110.        What does conjugation require?
Definition
110.        cell to cell contact and specific surface proteins
Term
111.        T/F Conjugation is not DNase resistant.
Definition
111.        F – it is DNase resistant
Term
112.        How is the ability to promote conjugation usually endoded?
Definition
112.        by a plasmid in the donor cell
Term
113.        What are plasmids?
Definition
113.        covalently closed, circular, supercoiled DNA molecules that replicate autonomously
Term
114.        How are plasmids inherited?
Definition
114.        stably in an extrachromosomal state
Term
115.        Are plasmids essential?
Definition
115.        No, they are “extra DNA” sometimes lost
Term
116.        What are a few types of genes that plasmids can carry?
Definition
116.        antibiotic resistance, toxin production, metal ion resistance, virulence factors, bacteriocin production, etc.
Term
117.        What is the Incompatibility property of plasmids?
Definition
117.        prevents 2 related plasmids from stably replicating in the same cell
Term
118.        What prevents entry of a plasmid into a cell that already had a closely related plasmid?
Definition
118.        Surface exclusion
Term
119.        Are unrelated plasmids affect by Incompatibility and Surface exclusion?
Definition
119.        No
Term
120.        What is the Host Range?
Definition
120.        host in which a plasmid can replicate
Term
121.        How is the copy number determined?
Definition
121.        by the plasmid replication system, no the plasmid size
Term
122.        T/F – Often small plasmids have a high copy number whereas large plasmids usually have a low copy number.
Definition
122.        T
Term
123.        What type of plasmids have the ability to promote their own transfer from one cell to another?
Definition
123.        Conjugative plasmids
Term
124.        Are Non-conjugative plasmids able to promote their own transfer?
Definition
124.        No
Term
125.        What are the 2 types of non-conjugative plasmids?
Definition
125.        Mobilizable and Non-mobilizable
Term
126.        How are mobilizable plasmids transferred?
Definition
126.        can’t transfer themselves but can be mobilized to transfer by another conjugative plasmid in the same cell.
Term
127.        How are Mobilizable plasmids classified?
Definition
127.        oriT+
Term
128.        T/F Non-mobilizable plasmids can’t transfer under any condition.
Definition
128.        T – they are oriT (origin of transfer) defective
Term
129.        What confers the ability of F factor of E. Coli to integrate into the host chromosome?
Definition
129.        IS sequences
Term
130.        What type of cells are good recipients for DNA transfer by conjugation because they have no F factor?
Definition
130.        F-
Term
131.        What type of cells have an extrachromosomal F factor?
Definition
131.        F+
Term
132.        Which type of cells have the F factor integrated into the chromosome?
Definition
132.        Hfr
Term
133.        How is the F Factor in the F’ cell?
Definition
133.        the extrachromosomal F factor also carries some chromosomal genes incorporated during aberrant excision of an integrated plasmid
Term
134.        What are the steps in Transfer of an F Plasmid by conjugation?
Definition
134.        1) F pilus of donor cell contact recipient cell, pulls it in; 2) conjugation bridge formed, plasmid DNA nicked at oriT; 3) DNA replicated by rolling circle replication, 5’ end transferred through conjugation bridge, complementary strand made; 4) complete transferred plasmid circularizes and become stable; 5) Conjugation bridge breaks.
Term
135.        What are the steps of Chromosomal DNA transfer by an Hfr?
Definition
135.        1) Hfr cell contacts recipient (F-) cell with F pilus, forms conjugation bridge; 2) Nicking oriT, rolling circle replication, 5’ end transferred; 3) conjugation bridge breaks before circularization sequence is transferred; 4) Transferred strand find homologue in recipient chromosome and recombines into it.
Term
136.        How does Conjugation occur in Gram-Positive bacteria?
Definition
136.        recipient cells make small peptide pheromones, causing donor cells to make adhesions and cells clump, conjugation bridges form.
Term
137.        T/F pheromones are specific for plasmids.
Definition
137.        T
Term
138.        What can the IS element serve as?
Definition
138.        a region of homology for recombination into the host chromosome
Term
139.        How can homologous recombination lead to excision or inversion of the intervening DNA?
Definition
139.        depending on the relative IS orientation
Term
140.        How does Amplification of Resistance work?
Definition
140.        Increased number of drug resistance genes integrated into the cell confer resistance to a higher concentration of antibiotics
Term
141.        What are integrons?
Definition
141.        discrete DNA elements that carry promoterless antibiotic resistance genes
Term
142.        How do integrons integrate?
Definition
142.        specific sites and do not encode a transposase
Term
143.        More multi-drug resistant plasmids may be generated by what?
Definition
143.        Integrons
Term
144.        What are bacteriophages?
Definition
144.        viruses that infect bacteria
Term
145.        How are phages organized?
Definition
145.        particles are composed of a single molecule of nucleic acid which is protected by a protein coat.
Term
146.        What are the 2 types of Lifestyles phages can take?
Definition
146.        Virulent and Temperate
Term
147.        What lifestyle results in the production of more phage particles through lytic development?
Definition
147.        Virulent
Term
148.        What 2 outcomes can result from a Temperate Phage?
Definition
148.        1) lytic development and progeny phage production. 2) formation of lysogen containing a repressed prophage.
Term
149.        What is used by phages for adsorbing to their host cells?
Definition
149.        tails
Term
150.        What are the steps in Lytic Development?
Definition
150.        1) Adsorption; 2) Injection of DNA; 3) Transcription of phage DNA; 4) Phage proteins made, phage DNA replicated, conversion of bacterium to phage factory; 5) “Factory” produces Phage structures; 6) DNA packaged into phage; 7) Lysis … Repeat
Term
151.        How can phages be detected in an agar plate?
Definition
151.        formation of plaque
Term
152.        What are the steps in Lysogen Formation with Integration?
Definition
152.        1) Phage DNA injected into bacterium; 2) Lytic functions turned off in phage mRNA synthesis by Repressor; 3) Phage DNA molecule inserted into chromosome of bacterium by Integrase protein; 4) bacterium grows and divides with phage genes as part of bacterial chromosome
Term
153.        T/F – Lysogen Formation with Replication as a Plasmid integrates the phage DNA into the bacterial DNA.
Definition
153.        F – There is no integrase or integration, the phage DNA replicates at a low level as a plasmid
Term
154.        How does Induction of an integrated prophage or a plasmid prophage take place?
Definition
154.        destruction of the phage repressor protein
Term
155.        T/F – All Lysogens are immune to superinfection
Definition
155.        T
Term
156.        What can lysogenic conversion do?
Definition
156.        alter cell wall properties and provide new phage resistances
Term
157.        What phage of C. diphtheria carries the tox gene which encodes diphtheria toxin?
Definition
157.        temperate phage β
Term
158.        What phage encodes for SPE’s responsible for scarlet fever?
Definition
158.        Phage T12
Term
159.        What phage encodes a Shiga-like toxin?
Definition
159.        Phage H19B
Term
160.        T/F – Infection by a non-toxigenic strain of C. botulinum with a phage that encodes a toxin can convert the strain to a virulent strain that produces the toxin.
Definition
160.        T
Term
161.        What is Transduction?
Definition
161.        the transfer of genetic material by a phage particle
Term
162.        What are the 2 types of Transduction?
Definition
162.        Generalized and Specialized
Term
163.        Which type of Transduction occurs by mistaken packaging of a piece of host DNA into a phage particle instead of a phage DNA?
Definition
163.        Generalized
Term
164.        How does Specialized Transduction occur?
Definition
164.        aberrant excision of a prophage leading to incorporation of a small piece of host DNA into the phage genome
Term
165.        What is abortive transduction?
Definition
165.        formation of microcolonies instead of normal-sized colonies because the transduced DNA circularizes and only passed to 1 of 2 daughter cells.
Term
166.        What does Excision of Lambda DNA require?
Definition
166.        integrase and XIS proteins
Term
167.        What is Lambda integration catalyzed by?
Definition
167.        λ integrase protein
Term
168.        What are λdgal phages defective for?
Definition
168.        growth and plaque formation
Term
169.        What is provided to help the phages with missing function grow?
Definition
169.        helper phage
Term
170.        What are High Frequency Transducing lysate (HFT)?
Definition
170.        a transductant that arises by lysogenization with both a transducing phage and a normal helper phage
Term
171.        What is the size of DNA transferred by Transduction?
Definition
171.        1-2% of the chromosome
Term
172.        What transfers medium sized pieces of DNA, 5-10% of chromosome?
Definition
172.        Transformation
Term
173.        How big are pieces of DNA that are transferred with conjugation?
Definition
173.        25-50% of chromosome
Term
174.        What is a Transposable element?
Definition
174.        discrete segments of DNA that move from one site to another in a genome without a requirement for DNA sequence homology
Term
175.        What is Transposition catalyzed by?
Definition
175.        transposase enzyme
Term
176.        What do all transposable elements (TE) have?
Definition
176.        short (15-30bp) inverted repeats
Term
177.        What are a type of TE with short inverted repeats at ends and no detectable phenotypes?
Definition
177.        Insertion sequences, IS
Term
178.        What are Type 1 composite transposons?
Definition
178.        large elements with long repeats at the ends and unique DNA in the middle, usually antibiotic resistance
Term
179.        Which type of TE has ends that cannot transpose independently?
Definition
179.        Tn3-like transposons
Term
180.        What type of TE has the ability to cause mutation by insertion into host genes?
Definition
180.        Mu bacteriophage
Term
181.        What part of the TE binds the transposase?
Definition
181.        short inverted repeats at the ends
Term
182.        How can insertion into a gene disrupt the gene function?
Definition
182.        can eliminate function of downstream genes by polarity
Term
183.        How does simple transposition work?
Definition
183.        Tn from replicon 1 adds on to replicon 2
Term
184.        What happens in Replicative transposition?
Definition
184.        cointegration
Term
185.        How does Replicative transposition and resolution work?
Definition
185.        R1 and R2 add together and replicate and cointegrate, then separate back down to separate R1 and R2 each with Tn.
Term
186.        T/F – conjugative transposons can transfer between Gram+ and Gram- bacterial species.
Definition
186.        T
Term
187.        What are some examples of Diagnostic Methods?
Definition
187.        Direct Examination, Culture, Antibody Detection, Detection of Microbial Components or Metabolites, Genome Detection
Term
188.        How can a direct specimen be taken?
Definition
188.        when pathogen is located in an otherwise sterile site, abscess, collected surgically or by needle aspiration
Term
189.        What is a specimen called that is in a sterile site but must pass through a site containing normal flora to be collected?
Definition
189.        Indirect Sample
Term
190.        How is a Sample taken from a site with normal flora?
Definition
190.        Sample collected is a mixture, normal flora are inhibited under growth conditions for analysis.
Term
191.        What are a few guidelines for Specimen Selection, Collection, and Transport?
Definition
191.        Select from active infection, minimize contamination, collect before antimicrobial therapy, minimize time from collection to assay…. etc.
Term
192.        How does an Agglutination Assay work?
Definition
192.        Antibody is bound by its Fc receptor end to the protein A on the surface of dead Staph. A. Visible agglutination is produced when these particles combine with a soluble antigen or another particulate antigen.
Term
193.        How does Direct Immunofluorescence work?
Definition
193.        1) Acetone-fixed cells on slide; 2) Add fluorescein-conjugated antiserum and incubate; 3) Wash unattached antibody; 4) Exam for fluorescence under UV illumination
Term
194.        What is different about Indirect Immunofluorescence?
Definition
194.        Rabbit antibody added first which is pathogen specific, then fluorescein-labeled goat anti-rabbit antibody is added, then viewed under UV light.
Term
195.        What type of enzymes are used in Enzyme-linked Assays?
Definition
195.        Horseradish peroxidase, Alkaline Phosphatase, Beta-galactosidase
Term
196.        How are ELISA Assays reported?
Definition
196.        titer reported is the highest serum dilution that still gives a detectable Ag-Ab reaction based on the color observed.
Term
197.        What is the Western Blot used for in detection of Anti-HIV Ab in serum?
Definition
197.        Distiguishes false positive ELISA vs True positive
Term
198.        Why are DNA Probes convenient for detection?
Definition
198.        Probe is pathogen specific and commercially available.
Term
199.        What are some advantages of PCR?
Definition
199.        more sensitive than direct hybridization, need very small amount of DNA in specimen, very fast
Term
200.        What are some disadvantages of PCR?
Definition
200.        Expense, false positives, false negatives
Term
201.        When should PCR be used?
Definition
201.        for pathogens with no existing test, poor tests, or diseases with low antigen and antibody production
Term
202.        What are some examples of pathogens that PCR is used to detect?
Definition
202.        hepatitis B, Chlamydia trachomatis, Neisseria gonorrhoeae, HIV, Lyme disease
Term
203.        What does Amplicon Detection by Real-Time PCR use?
Definition
203.        DNA intercalating dyes or fluorogenic DNA probes
Term
204.        How is contamination reduced in Amplicon Detection by R-T PCR?
Definition
204.        Amplification and detection are done simultaneously in a closed system.
Term
205.        Order the following from fastest to slowest time it takes for results:
Definition
205.        C, F, D, A, E, B
Term
206.        What is a virus?
Definition
206.        Obligate intracellular parasites that replicate by self-assembly of individual components rather than by binary fission.
Term
207.        Can Viruses make energy or proteins by themselves?
Definition
207.        No
Term
208.        T/F – viruses contain a genome with RNA and DNA.
Definition
208.        F – contain a genome of limited size that is either RNA or DNA, never both.
Term
209.        How are viruses classified?
Definition
209.        1. Size; 2. morphology; 3. type of genome; 4. mechanism of replication. (physical and biochemical characteristics)
Term
210.        How can virus genomes be structured?
Definition
210.        1. circular or linear ss RNA
Term
211.        What is the protein shell that packages the virus genome?
Definition
211.        capsid
Term
212.        What 3 forms can capsids be in?
Definition
212.        icosahedral (spherical) , helical, complex
Term
213.        Capsids are the result of self-assembly of what?
Definition
213.        virally-encoded capsomeres
Term
214.        How is the shape of the capsid dictated?
Definition
214.        by the capsomeres that self-assemble, not the shape of the genome.
Term
215.        What makes up a nucleocapsid?
Definition
215.        genome + capsid
Term
216.        Why are enveloped viruses less stable than naked viruses?
Definition
216.        a. more susceptible to drying
Term
217.        How do enveloped viruses spread?
Definition
217.        large droplets, secretions, organ transplants, blood transfusions.
Term
218.        How many families of DNA viruses are there? RNA viruses?
Definition
218.        6; 14
Term
219.        What are the major steps in viral replication?
Definition
219.        1. attachment
Term
220.        What are the 6 viral cytopathogenesis?
Definition
220.        1. Inhibition of cellular protein synthesis
Term
221.        Can the +RNA virus genome function as mRNA?
Definition
221.        Yes – and is immediately translated by cellular ribosomes
Term
222.        How are –RNA virus genomes used?
Definition
222.        must be used as a template to transcribe a +RNA strand
Term
223.        How do retroviruses function?
Definition
223.        carry a RNA-dependent DNA polymerase (reverse transcriptase), +RNA genome is reverse transcribed into dsDNA and integrated into host genome
Term
224.        How are DNA virus genomes transcribed?
Definition
224.        By host DNA-dependent RNA polymerase
Term
225.        What do viruses use to redirect host polymnerases to viral genes and away from cellular genes?
Definition
225.        specific transcription factors
Term
226.        What do larger viruses depend of for viral genome replication?
Definition
226.        virally-encoded DNA-dependent DNA polymerases
Term
227.        Do smaller viruses need this?
Definition
227.        No, they use host DNA polymerase
Term
228.        How are plaques formed?
Definition
228.        virus infected cells are lysed and leave a “hole” in a confluent monolayer
Term
229.        What is a lysate?
Definition
229.        the suspension of virions in culture medium that results from unrestricted growth of the virus on a cell monolayer
Term
230.        T/F – all virus particles produced in a lysate are infectious.
Definition
230.        F – particle-to-pfu ratio measure the number of physical particles compared to the number of infectious virions
Term
231.        What do Plaque assays measure?
Definition
231.        the number of infectious virions in a given volume of lysate.
Term
232.        What is the Multiplicity of Infection (MOI)?
Definition
232.        the ratio of the number of infectious particles to the number of target cells to be infected.
Term
233.        What MOI is needed to ensure that all cells are infected?
Definition
233.        between 5-10
Term
234.        What corresponds to the eclipse period of the single-cycle growth curve?
Definition
234.        post-penetration phase until virus can be detected intracellulary; corresponds to uncoating, early transcription, and genome replication steps;
Term
235.        When does the eclipse period end?
Definition
235.        a Virus assembly
Term
236.        When does the latent period take place?
Definition
236.        post-penetration phase until virus can be detected extracellularly
Term
237.        What does the latent period correspond to?
Definition
237.        uncoating, early transcription, genome replication, virus assemble, and release
Term
238.        T/F – the latent period includes the eclipse period.
Definition
238.        T
Term
239.        Why do viral mutation occur at high frequencies?
Definition
239.        large number of genome copies produced in every infected cell, and polymerase errors
Term
240.        What step of viral genetics involves exchange of proteins?
Definition
240.        Complementation
Term
241.        What happens in Recombination?
Definition
241.        An exchange of genetic material on the same segment of genome.
Term
242.        Does recombination occur with both DNA and RNA?
Definition
242.        DNA – yes occurs frequently
Term
243.        What is the process called that is an exchange of genetic material on different segments of genome?
Definition
243.        Reassortment
Term
244.        What are some things to consider about virus-host interactions?
Definition
244.        route of transmission, secondary spread, incubation period, acute vs. persistent infection, control
Term
245.        What is the most common rout of infection?
Definition
245.        inhalation
Term
246.        What are 2 ways viruses are spread?
Definition
246.        release of virus from infected cell or syncytia formation
Term
247.        What is syncytia formation?
Definition
247.        enveloped viruses can fuse an infected cell with uninfected cells to directly spread to surrounding cells
Term
248.        What is viremia?
Definition
248.        presence of virions in blood
Term
249.        What is the minimum incubation period for viruses that require secondary spread?
Definition
249.        12-14 days
Term
250.        T/F – patients can be infection during the incubation period.
Definition
250.        T
Term
251.        What phase of an infection is the symptomatic phase?
Definition
251.        acute phase
Term
252.        What are the 3 froms of persistent infection?
Definition
252.        Chronic, latent, transforming
Term
253.        What is an example of a latent virus? transforming virus?
Definition
253.        herpes; HPV, HIV
Term
254.        What is the first defense in nonspecific immune response?
Definition
254.        natural killer cells and IFN
Term
255.        What are 3 types of antivirals available?
Definition
255.        vaccines, immune globulin, drugs
Term
256.        What are the 3 basic types of viral vaccines?
Definition
256.        live, attenuated virus; killed virus; subunit (recombinant DNA)
Term
257.        What is the challenge of antiviral drugs?
Definition
257.        viruses are parasites and use much of our own cellular processes, Drugs toxic to Viruses can be toxic to us.
Term
258.        What drug inhibits uncoating of picornaviruses?
Definition
258.        Disoxaril
Term
259.        What drug inhibits uncoating of influenza A and how does it work?
Definition
259.        amantadine and rimantadine; inhibits a viral ion channel
Term
260.        What does IFN-alpha inhibit in hepatitis B and C and HPV?
Definition
260.        transcription and translation
Term
261.        How is translation of CMV mRNA inhibited?
Definition
261.        a specific antisense RNA
Term
262.        What do the majority of antivirals target and what are they composed of?
Definition
262.        DNA replication; nucleotide analogs that inhibit viral DNA polymerases or prevent chain elongation
Term
263.        How do protease inhibitors work?
Definition
263.        prevent polyprotein cleavage and virus assembly by acting as alternative substrates
Term
264.        What does ribavirin do?
Definition
264.        inhibits nucleoside biosynthesis and as a result inhibits mRNA cap formation and inhibits some RNA polymerases.
Term
265.        What is ribavirin used for?
Definition
265.        Hepatitis C, Flu and respiratory syncytial virus
Term
266.        What inhibits flu A and B neuraminidase?
Definition
266.        Relenza and Tamiflu
Term
267.        What do inhibitor cocktails do?
Definition
267.        decrease the chances of encountering a resistant strain
Term
268.        T/F – Combination therapies appear to be synergistic.
Definition
268.        T
Supporting users have an ad free experience!