VBS Exam 4 Labs Questions and
Answers
What is the difference between PCR and RT-PCR? - answerPCR is the diagnostic test
with the highest sensitivity and specificity (DNA, primers that bind to sequence of
interest, dNTPs, buffer, heat-stable DNA polymerase- Taq polymerase)
RT-PCR is used when a sample contains RNA rather than DNA. Reverse transcriptase
is isolated from a retrovirus and must first copy the RNA into DNA
What is the difference between PCR and qPCR? - answerqPCR=quantitative, involves
SYBR green or TaqMan reagents which includes a fluorescent dye that can be
automatically quantitated, more scalable.
PCR is performed on agarose gels with stains that bind to DNA. labor intensive, cannot
quantitate how much DNA or RNA in the original sample
Why is it useful to have the NCBI database as a resource for the whole world? -
answerunderstanding and discovery of new biological insights from complex datasets.
Define false positives and false negatives. How would these relate to determining the
suitability of a primer set for detection of SARS-CoV-2? - answershould be highly
specific
Why are G-C pair bonds stronger? - answer3 hydrogen bonds rather than 2
Which tests are used to further characterize Gram positive bacteria? - answercatalase,
coagulase, blood hemolysis, bile esculin
Which tests are used to further characterize Gram negative bacteria? - answeroxidase,
indole, MRVP, MAC
what do CNA plates select for? differentiate between? - answergram positive; alpha,
beta, gamma hemolysis
what do MAC plates select for? differentiate between? - answergram negative; lactose
fermentors and non-fermentors
what do MSA plates select for? differentiate between? - answergram positive; mannitol
fermentors and non-fermentors
What does serology detect - answersingle protein/carbohydrate
indicates absence or presence
, ex: rapid strep test
What does MALDI-TOF Mass Spectrometry detect? - answerMultiple abundant proteins
identify genus and species by comparing it to known protein profiles, rapid
What does Nucleic acid (DNA, RNA) detect? - answerGene/sequence via PCR
sequencing detects everything in sample, compare to known sequences to identify
genus, species, strain, differences
rapid
Ex: PCR
What can biochemical tests test for? - answermetabolic capability: fermentation, carbon
source, catalase, other enzymes
a culture: MacConkey plates, catalase test, blood agar plates
What do MacConkey plates differentiate and select for? - answerselect for gram
negative, differentiate lactose fermentors and non-fermentors
blood agar plates select for and differentiate between what? - answerselect from gram
positive; differentiate alpha, beta, gamma hemolysis
What does CNA select and differentiate for? - answerselects for gram-positive
differentiates by hemolytic reaction (alpha, beta, gamma)
what does CNA stand for and what do they contain - answerColumbia Nalidixic Acid
agar
contains colistin and nalidixic acid; and sheep red blood cells
What does MAC select and differentiate for? - answerselects for gram-negative plates,
differentiates lactose fermentors and non-fermentors
what do MAC plates inhibit? - answerselects against gram + and inhibits growth of
organisms not adapted to the gut environment
What do MAC plates contain - answercrystal violet and bile salts
Why does differentiation for lactose fermentation occur in MAC plates? What color are
the colonies if they ferment lactose? - answerlactose fermentation produces acid
byproducts that lower pH and turn the pH indicator pink.
Lactose fermenters turn pink; non-lactose fermenter form off-white colonies
What are some common examples of gram positive bacteria - answerstaphylococcus,
streptococcus, enterococcus
Tests for gram positive bacteria - answercatalase, coagulase, blood hemolysis pattern,
bile esculin
Answers
What is the difference between PCR and RT-PCR? - answerPCR is the diagnostic test
with the highest sensitivity and specificity (DNA, primers that bind to sequence of
interest, dNTPs, buffer, heat-stable DNA polymerase- Taq polymerase)
RT-PCR is used when a sample contains RNA rather than DNA. Reverse transcriptase
is isolated from a retrovirus and must first copy the RNA into DNA
What is the difference between PCR and qPCR? - answerqPCR=quantitative, involves
SYBR green or TaqMan reagents which includes a fluorescent dye that can be
automatically quantitated, more scalable.
PCR is performed on agarose gels with stains that bind to DNA. labor intensive, cannot
quantitate how much DNA or RNA in the original sample
Why is it useful to have the NCBI database as a resource for the whole world? -
answerunderstanding and discovery of new biological insights from complex datasets.
Define false positives and false negatives. How would these relate to determining the
suitability of a primer set for detection of SARS-CoV-2? - answershould be highly
specific
Why are G-C pair bonds stronger? - answer3 hydrogen bonds rather than 2
Which tests are used to further characterize Gram positive bacteria? - answercatalase,
coagulase, blood hemolysis, bile esculin
Which tests are used to further characterize Gram negative bacteria? - answeroxidase,
indole, MRVP, MAC
what do CNA plates select for? differentiate between? - answergram positive; alpha,
beta, gamma hemolysis
what do MAC plates select for? differentiate between? - answergram negative; lactose
fermentors and non-fermentors
what do MSA plates select for? differentiate between? - answergram positive; mannitol
fermentors and non-fermentors
What does serology detect - answersingle protein/carbohydrate
indicates absence or presence
, ex: rapid strep test
What does MALDI-TOF Mass Spectrometry detect? - answerMultiple abundant proteins
identify genus and species by comparing it to known protein profiles, rapid
What does Nucleic acid (DNA, RNA) detect? - answerGene/sequence via PCR
sequencing detects everything in sample, compare to known sequences to identify
genus, species, strain, differences
rapid
Ex: PCR
What can biochemical tests test for? - answermetabolic capability: fermentation, carbon
source, catalase, other enzymes
a culture: MacConkey plates, catalase test, blood agar plates
What do MacConkey plates differentiate and select for? - answerselect for gram
negative, differentiate lactose fermentors and non-fermentors
blood agar plates select for and differentiate between what? - answerselect from gram
positive; differentiate alpha, beta, gamma hemolysis
What does CNA select and differentiate for? - answerselects for gram-positive
differentiates by hemolytic reaction (alpha, beta, gamma)
what does CNA stand for and what do they contain - answerColumbia Nalidixic Acid
agar
contains colistin and nalidixic acid; and sheep red blood cells
What does MAC select and differentiate for? - answerselects for gram-negative plates,
differentiates lactose fermentors and non-fermentors
what do MAC plates inhibit? - answerselects against gram + and inhibits growth of
organisms not adapted to the gut environment
What do MAC plates contain - answercrystal violet and bile salts
Why does differentiation for lactose fermentation occur in MAC plates? What color are
the colonies if they ferment lactose? - answerlactose fermentation produces acid
byproducts that lower pH and turn the pH indicator pink.
Lactose fermenters turn pink; non-lactose fermenter form off-white colonies
What are some common examples of gram positive bacteria - answerstaphylococcus,
streptococcus, enterococcus
Tests for gram positive bacteria - answercatalase, coagulase, blood hemolysis pattern,
bile esculin
