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1. You know that PCR uses heat resistant enzymes. We used Taq polymerase, but there are a number of heat resistant DNA polymerases that can be used. One big difference that is seen is the fidelity, or proofreading ability. Proofreading ability lowers the number of mistakes that the polymerase makes during the extension step of PCR. Taq does not proofread.

a. Why is Taq’s lack of proofreading ability not important for the purpose of this lab? (1 pt.)

b. Provide an example of where it would be important to use a polymerase that does have proofreading capability. (1 pt.)

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Bunny GreenfelderLv2
28 Sep 2019
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Related questions

1. In addition to identifying the genetic material, the experiments of Avery, MacLeod, and McCarty with different strains of Streptococcus pneumoniae demonstrated that
DNA is a double helix.
DNA may be taken up by bacterial cells and be active.
DNA is present in bacteriophage T2.
eukaryotic cells may be genetically transformed.
DNA binds to the cell wall of the bacterium.
2. In order to show that DNA in cell extracts is responsible for genetic transformation in Streptococcus pneumoniae, important corroborating evidence should indicate that _______ also destroy transforming activity.
temperatures high enough to kill cells
enzymes that hydrolyze proteins
enzymes that hydrolyze DNA
enzymes that hydrolyze polysaccharides
enzymes that hydrolyze RNA
3. Based on what you have learned about the experiments conducted by Griffith and Avery and colleagues with bacteria, which of the following would result in transformation of living R cells?
Pure RNA from S cells
Cell-membrane extracts from S cells
A mixture of pure RNA and protein from S cells
Cell-free extracts from S cells
Pure protein from S cells
4. A-T base pairs in a DNA double helix
form three hydrogen bonds with each other.
are more heat-stable than G-C base pairs.
are of a substantially different length than G-C base pairs.
are not accessible to DNA binding proteins.
are chemically distinct from G-C base pairs.
5. If 23 percent of the bases in a sample of double-stranded DNA are adenine, what percentage of the bases are uracil?
27
50
0
73
23
6. The uniform diameter of the DNA structure provides evidence for
antiparallel DNA strands.
a right-handed helix.
a double-stranded helix.
3′ end phosphorylation.
purine–pyrimidine pairing.
7. If a sequence of one strand of DNA is 5′-TGACTATC-3′, what is the complementary strand?
5′-ACTGATAG-3′
3′-TGACTATC-5′
3′-ACTGATAG-5′
3′-ACTGATAG-3′
5′-TGACTATC-3′
8. What structural aspect of the DNA facilitates dissociation of the two DNA strands for replication?
3′ end phosphorylation
Purine–pyrimidine pairing
Antiparallel DNA strands
Covalent bonds between sugars and phosphate groups
Hydrogen bonding between paired bases
9. If the Meselson–Stahl density gradient experiment had resulted in two bands of DNA molecules after only one round of replication, one containing only 15N and the second only 14N, this result would have indicated that replication was
unidirectional.
dispersive.
conservative.
bidirectional.

semiconservative.
10. The nucleoside analogue acyclovir, which is used to treat herpes simplex virus (HSV) infections, lacks a 3′ hydroxyl group (–OH). Predict what will happen if the host cell DNA polymerase incorporates a molecule of acyclovir into an elongating strand of HSV DNA.
The replication complex will no longer bind to origins of replication.
The DNA polymerase will only incorporate acyclovir molecules.
Acyclovir will bind single-strand binding proteins.
DNA polymerase will not be able to link a successive nucleotide.
Acyclovir will block the activity of the DNA helicase.
11. Which of the following does not demonstrate the stability of the DNA double helix?
Single-strand binding proteins are required to keep the strands apart.
Paired bases form hydrogen bonds.
High temperatures are required to denature it.
DNA synthesis requires energy.
DNA helicases require ATP.
12. What effect would a primase inhibitor have on DNA replication?
DNA polymerase would not be able to add bases to the DNA.
Primase would be blocked from joining the DNA replication complex.
Primase would not be able to provide primers for DNA polymerases.
DNA polymerase would not be able to use DNA as a template.
There would be no effect on DNA replication.
13. To replicate their DNA in a timely manner, most eukaryotic chromosomes
normally have uncoiled DNA.
have multiple origins of replication.
contain linear molecules of single-stranded DNA.
have two replication forks that move in the same direction.
are composed entirely of DNA.
14. Which statement about DNA replication is false?
Okazaki fragments are synthesized as parts of the leading strand.
Error rates for DNA replication are reduced by proofreading of the DNA polymerase.
The sliding clamp increases the rate of DNA synthesis.
Replication forks represent areas of active DNA synthesis on the chromosomes.
Ligases and polymerases function in the vicinity of replication forks.
15. In many eukaryotes, there are repetitive sequences called telomeres at the ends of chromosomes. After successive rounds of DNA replication, the _______ strand becomes shorter. In some cells, an enzyme called _______ repairs the shortened strand.
leading; telomerase
lagging; telomerase
lagging; DNA polymerase I
leading; DNA polymerase I
leading; replicase
16. A researcher studies normal human fibroblast cells. They can be maintained in culture but die off after about 30 cell generations. Unexpectedly, a colony of cells continues to survive and divide past 30 generations. Which scenario is most likely true for these cells?
DNA polymerase is constantly active.
Primase is able to extend the telomeres.
The mismatch repair system is extra efficient.
The telomerase gene is being expressed.
The cells do not need the ends of their chromosomes.
17. If DNA polymerase III introduces an incorrect nucleotide, what is the first corrective action made by the DNA repair system?
The replication complex excises the incorrect nucleotide.
The excision repair proteins remove the incorrect nucleotide.
The mismatch repair system scans for base-pairing mismatches.
There is no correction, because nucleotide errors by DNA polymerases are not repaired.
DNA ligase connects the correct nucleotide.
18. Choose the correct order of the following four events in the excision repair of DNA:
(1) Base-paired DNA is made complementary to the template.
(2) Damaged bases are recognized.
(3) DNA ligase seals the new strand to existing DNA.
(4) Part of a single strand is excised.
1, 2, 3, 4
2, 1, 3, 4
3, 4, 2, 1
2, 4, 1, 3
4, 2, 3, 1
19. Six complete cycles of PCR should result in a _______-fold increase in the amount of DNA.
64
32
12
128
6
20. When double-stranded DNA is heated to temperatures above 90°C, it denatures. Denaturation is a process that
breaks covalent bonds.
hydrolyzes DNA.
separates double-stranded DNA into two single strands.
causes new hydrogen bonds to form.
irreversibly destroys the double helical structure.

Evaluation of PCR product electrophoresed on a 0.8% agarose gel shows non-specific bands. The appropriate modification for the next PCR reaction is toa )increase the concentration of Taq polymerase.b) increase the number of PCR cycles.c) decrease the template denaturation temperature.d) reduce the concentration of primers.In the Sanger sequencing method, chain termination is the result ofa)misincorporation of dUTP instead of dTTP.b)incorporation of ddGTP.c)secondary structures in the template strand.d)sequencing through repeats.The purpose of EDTA in a DNA storage buffer is toa)maintain single strands.b)bind magnesiumc)activate DNases.d)dissolve DNA into solution.The thermal cycler ramp refers to thea)degree of incline of the machine on the laboratory bench.b)gradient between denaturation and annealing temperature.c)programming key to set number of PCR cycles.d)amount of time required to reach the desired temperature.Evaluation of a blood sample indicates the presence of a clot. Corrective action to salvage this specimen for analysis would most likely requirea)digestion with proteinase K.b)homogenizing the sample under UV irradiation.c)removal of the clot with urea.d)requesting a new sample immediately.Incorporation of biotin into template DNA by nick-translation requiresa)DNase.b)ligase.c)random hexanucleotides.d)3 temperatures.An isolated DNA sample is viscous, difficult to pipet, and will not resuspend in TE buffer after rehydration at 37C for 24 hours. The most appropriate step is toa)digest the DNA with a frequent cutting restriction enzyme.b)re-extract the original sample with higher volumes of reagents.c)increase the rehydration temperature to 95C.d)add more TE buffer.Excess glycerol in a restriction digestion reaction results ina)enzyme degradation.b)diminished enzyme activity.c)increased temperature required for digestion.d)decreased enzyme buffer pH.Primer dimers will most likely be a result of PCR whena)3' and 5' primers are designed as 50% GC.b)DNA template concentration is very low.c)enhancing agents are added to the master mix.d)template DNA is initially denatured completely.Correct operation of a pH meter requiresa)calculation of the electrode millivolt equivalents.b)standardization of the meter with a range of buffers.c)documentation of absorbance and standard deviation.d)verification of pH readings with calf thymus DNA.The uracil DNA glycosylase pre-PCR decontamination procedure failed. The most likely cause of the failure is thea)enzyme solution was heated prior to PCR.b)enzyme buffer solution was alkaline pH.c)N-glycosidic DNA bonds cleaved after enzyme treatment.d)PCR was performed with dTTP instead of dUTP.The real-time PCR analysis does not show the characteristic melting curve for the patient or control samples. The fluorimetry readings of the PCR products indicate the appropriate concentration of template was added to the real-time PCR reaction mix. Which of the following reagents was likely missing from the PCR master mix to account for this finding?a)SYBR Green Ib)template DNAc)DMSOd)5X Cresol RedWhich of the following conditions favor enhanced specificity of PCR?a)decrease in the concentration of dNTPsb)increase in the sodium chloride concentrationc)increase in the concentration of Taq polymerased)decrease in the ramp speed and temperatureWhich of the following compounds is an inhibitor of Taq polymerase?a)magnesiumb)hemoglobinc)DMSOd)betaineWhich of the following compositions of gels would allow for the efficient separation of linear DNA molecules in the range of 100 to 300 base pairs in length?a)0.3% agaroseb)1.0% agarosec)1.0% polyacrylamided)8.0% polyacrylamide4.92*10^4 cpm of a random primed 32P dCTP (3000 Ci/mmol) labeled oligonucleotide probe were precipitated from a 50 uL standard reaction by TCA and 5.28*10^4 cpm is the total cpm in the sample. What is the percent incorporation of radioactivity for this labeling reaction?a)1.86%b)46.50%c)93.00%d)98.40%The stock solution of HCl is 1M. How much stock solution is required to prepare 250 mL of 50 mM HCl?a)0.2 mLb)5 mLc)12.5 mLd)125 mLSpectroscopy measurement of a DNA sample isolated by salt extraction technique gave the following absorbance readings: A260 0.4032 A280 0.3765This sample is:a)acceptable for molecular testing.b)contaminated with salt.c)contaminated with protein.d)contaminated with high amounts of RNA.What is the dilution factor if 50 uL of blood is diluted with 950 uL of saline?a)19b)20c)40d)50Which of the following are used to prepare a 0.9% agarose gel?a)0.9 g agarose + 100 mL distilled waterb)0.9 g agarose + 100mL TAEc)9 g agarose + 100mL TBEd)90 g agarose + 100 mL bufferThe concentration of double-stranded DNA with an optical density reading of 1.0 isa)0.5 ug/ulb)1.0 ug/ulc)10 ng/uld)50 ng/ulHow much Tris base (MW 121.1) would be required to make 4 liters of Tris-EDTA buffer that is 15 mM Tris?a)0.7266 gramsb)0.1211 gramsc)1.8165 gramsd)7.266 grams

Evaluation of PCR product electrophoresed on a 0.8% agarose gelshows non-specific bands. The appropriate modification for the nextPCR reaction is to


a )increase the concentration of Taq polymerase.

b) increase the number of PCR cycles.

c) decrease the template denaturation temperature.

d) reduce the concentration of primers.


In the Sanger sequencing method, chain termination is the resultof


a)misincorporation of dUTP instead of dTTP.

b)incorporation of ddGTP.

c)secondary structures in the template strand.

d)sequencing through repeats.


The purpose of EDTA in a DNA storage buffer is to


a)maintain single strands.

b)bind magnesium

c)activate DNases.

d)dissolve DNA into solution.


The thermal cycler ramp refers to the


a)degree of incline of the machine on the laboratory bench.

b)gradient between denaturation and annealing temperature.

c)programming key to set number of PCR cycles.

d)amount of time required to reach the desired temperature.


Evaluation of a blood sample indicates the presence of a clot.Corrective action to salvage this specimen for analysis would mostlikely require


a)digestion with proteinase K.

b)homogenizing the sample under UV irradiation.

c)removal of the clot with urea.

d)requesting a new sample immediately.


Incorporation of biotin into template DNA by nick-translationrequires


a)DNase.

b)ligase.

c)random hexanucleotides.

d)3 temperatures.


An isolated DNA sample is viscous, difficult to pipet, and willnot resuspend in TE buffer after rehydration at 37C for 24 hours.The most appropriate step is to


a)digest the DNA with a frequent cutting restriction enzyme.

b)re-extract the original sample with higher volumes ofreagents.

c)increase the rehydration temperature to 95C.

d)add more TE buffer.


Excess glycerol in a restriction digestion reaction resultsin


a)enzyme degradation.

b)diminished enzyme activity.

c)increased temperature required for digestion.

d)decreased enzyme buffer pH.


Primer dimers will most likely be a result of PCR when


a)3' and 5' primers are designed as 50% GC.

b)DNA template concentration is very low.

c)enhancing agents are added to the master mix.

d)template DNA is initially denatured completely.


Correct operation of a pH meter requires


a)calculation of the electrode millivolt equivalents.

b)standardization of the meter with a range of buffers.

c)documentation of absorbance and standard deviation.

d)verification of pH readings with calf thymus DNA.


The uracil DNA glycosylase pre-PCR decontamination procedurefailed. The most likely cause of the failure is the


a)enzyme solution was heated prior to PCR.

b)enzyme buffer solution was alkaline pH.

c)N-glycosidic DNA bonds cleaved after enzyme treatment.

d)PCR was performed with dTTP instead of dUTP.


The real-time PCR analysis does not show the characteristicmelting curve for the patient or control samples. The fluorimetryreadings of the PCR products indicate the appropriate concentrationof template was added to the real-time PCR reaction mix. Which ofthe following reagents was likely missing from the PCR master mixto account for this finding?


a)SYBR Green I

b)template DNA

c)DMSO

d)5X Cresol Red


Which of the following conditions favor enhanced specificity ofPCR?


a)decrease in the concentration of dNTPs

b)increase in the sodium chloride concentration

c)increase in the concentration of Taq polymerase

d)decrease in the ramp speed and temperature


Which of the following compounds is an inhibitor of Taqpolymerase?


a)magnesium

b)hemoglobin

c)DMSO

d)betaine


Which of the following compositions of gels would allow for theefficient separation of linear DNA molecules in the range of 100 to300 base pairs in length?


a)0.3% agarose

b)1.0% agarose

c)1.0% polyacrylamide

d)8.0% polyacrylamide


4.92*10^4 cpm of a random primed 32P dCTP (3000 Ci/mmol) labeledoligonucleotide probe were precipitated from a 50 uL standardreaction by TCA and 5.28*10^4 cpm is the total cpm in the sample.What is the percent incorporation of radioactivity for thislabeling reaction?


a)1.86%

b)46.50%

c)93.00%

d)98.40%


The stock solution of HCl is 1M. How much stock solution isrequired to prepare 250 mL of 50 mM HCl?


a)0.2 mL

b)5 mL

c)12.5 mL

d)125 mL


Spectroscopy measurement of a DNA sample isolated by saltextraction technique gave the following absorbance readings: A2600.4032 A280 0.3765

This sample is:


a)acceptable for molecular testing.

b)contaminated with salt.

c)contaminated with protein.

d)contaminated with high amounts of RNA.


What is the dilution factor if 50 uL of blood is diluted with950 uL of saline?


a)19

b)20

c)40

d)50


Which of the following are used to prepare a 0.9% agarosegel?


a)0.9 g agarose + 100 mL distilled water

b)0.9 g agarose + 100mL TAE

c)9 g agarose + 100mL TBE

d)90 g agarose + 100 mL buffer


The concentration of double-stranded DNA with an optical densityreading of 1.0 is


a)0.5 ug/ul

b)1.0 ug/ul

c)10 ng/ul

d)50 ng/ul


How much Tris base (MW 121.1) would be required to make 4 litersof Tris-EDTA buffer that is 15 mM Tris?


a)0.7266 grams

b)0.1211 grams

c)1.8165 grams

d)7.266 grams

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