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Biology 1002B Lecture Notes - Lecture 8: Taq Polymerase, Thermophile, Base Pair

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rubyelephant434
8 Apr 2016
School
Western University
Department
Biology
Course
Biology 1002B
Professor
Tom Haffie

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Document Summary

Need to denature template dna give more energy than energy of hydrogen bonds keeping those strands together. High temperature and then lower it if you stay there long enough, the strands will re- anneal. Have high concentraions of two short primers that will anneal to one strand and the other. Raise temp to 72 and polymerase will add g,c,a,ts by extending in the 3" direcion. Polymerase needs free 3" end to catalyze this reacion (primer gets you a free 3" end) Denaturaion, annealing of primers, and then extension using taq polymerase. When irst started always had to add an enzyme. This changed when we used taq dna polymerase isolated from a thermophile so it has awesome acivity at 72 and is very heat stabile: do not need to add anymore enzyme won"t degrade. Pcr based on incredible speciicity of the primers. 16 base pairs long how speciic is that for a single gene.

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Related Questions

Please answer all

Why does a template-dependent DNA polymerase require a primer to initiate DNA synthesis?

DNA polymerase require 5' phosphate to add a new nucleotide

DNA polymerase require 3' hydroxyl group to add a new nucleotide

DNA polymerase require energy by hydrolizing the primers

Which of the following enzymes is template independent?

Reverse transcriptase

Klenow fragment

DNA polymerase

Terminal deoxynucleotidyl transferase

RNA polymerase

The natural function of a DNA ligase enzyme is:

Joining together DNA sequences with compatible cohesive ends from two different organisms to yield a recombinant DNA molecule

Sealing single stranded nicks in double stranded DNA molecules

Joining together two blunt ended fragments of DNA within a cell

Joining together two single stranded DNA molecules

The natural function of 3' -> 5' exonuclease activity of a DNA polymerase is to:

Remove the 5' end of the DNA strand that is being copied

Remove damaged nucleotide from the template strand

Remove nucleotides from the end of DNA to generate blunt ends

Remove incorrect nucleotides from the newly synthesized DNA

Which technique is used to resolve the different sizes of DNA fragments?

Gene cloning

PCR

DNA sequencing

Gel electrophoresis

Which of the following vectors does not contain bacterial origin of replication (oriC)?

plasmid

cosmid

bacterial artificial chromosome

lambda vector

Which process of bacteriophage is not used for gene cloning?

Concatemer formation

Lytic cycle

Lysogenic cycle

viral packaging

What vector would be best suited for creating a contig of bovine (cattle) chromosome 10?

lambda vector

Cosmid vector

P1 vector

Plasmid

E. coli takes up plasmid DNA by which of the following methods?

Transduction

Transformation

Conjugation

Transfection

The following times and temperatures are an example of the steps for PCR. You can use the Figure to help you answer the following questions.

Why is the first step is carried out at 94°C?

To degrade the template

To denature the template

To activate the polymerase

To facilitate the primer binding

What happens in the reaction when the temperature shifts to 55°C during cycling?

the DNA polymerase will carry out DNA synthesis by extending the annealed primers

the DNA polymerase will finish DNA synthesis

the primers anneal to the single-stranded regions of the DNA

the primers anneal to the double-stranded regions of the DNA

During cycling, what occurs when the temperature is at 72°C?

the primers anneal to the double-stranded regions of the DNA

the DNA polymerase will carry out DNA synthesis by extending the annealed primers

the primers anneal to the single-stranded regions of the DNA

the DNA polymerase will finish DNA synthesis

You designed a set of primers to amplify 1 kb DNA with polymerase chain reaction. By which cycle of polymerase chain reaction, we would expect to see the first double stranded DNA with expected size?

The end of cycle 1

The end of cycle 2

The end of cycle3

The end of cycle 4

Answered most of the questions. Can you tell me if my answers are correct? Last question of the month. Thank you. I appreciate it.

4. You perform electrophoresis on the product of a PCR and see that instead of the 300-base band you expected that there are five different bands.

What controls the specific sequence to which a PCR primer binds? Complementary sequence and annealing temperature control the specific sequence to which a PCR primer binds.

What are two factors that contribute to the annealing temperature of the primer? Two factors that contribute to the annealing temperature of the primer is primer length and the Guanine and Cytosine content.

What part of your thermal cycle protocol could you change, and how would you change it, to try and get rid of the extra bands?

To get rid of the extra band, we have to increase the annealing temperature.

If, after performing electrophoresis, there were no bands on the gel, what part of your thermal cycle protocol would you change, and how would you change it?

After performing electrophoresis, if there were no bands on the gel then we have to decrease the annealing temperature of the primer

5. If you are using a DNA sequence from a related species to design primers for your species of interest, why is it better to design your primers to complement an exon?

In related species there are similarities but their genetic makeup will not be the same. It is better to design your primers to complement an exon because ??

6. Why is it better to use a 25-base primer than a 10-base primer? Why do you have to have a lower annealing temperature for a 10-base primer?

It is better to use a 25-base primer than a 10-base primer because a 10-base primer is not long enough and may pair with a wrong portion of DNA, which would give wrong results. You have a lower annealing temperature for a 10-base primer because annealing temperature increases when the number of base pairs increase. If the temperature is too high the primer might not bind.

Identify the three steps in PCR and tell the function of each step.

Denaturation - when the double-stranded DNA is heated to 92-95℃ for about one minute, to separate it into two single strands.

Annealing - temperature of the reaction is lowered to a temperature that is between 45℃ and 65℃ to allow the DNA primers to attach to the template DNA.

Extension - temperature of the reaction is raised to a temperature between 45℃ and 65℃ and the new strand of DNA is made by adding nucleotides to the ends of the primers.

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.