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BIOLOGY 1A03 Lecture Notes - Lecture 18: Phosphodiester Bond, Pyrophosphate, Hydrogen Bond

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School
McMaster University
Department
Biology
Course
BIOLOGY 1A03
Professor
Lovaye Kajiura

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BIOLOGY 1A03 Full Course Notes
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BIOLOGY 1A03 Full Course Notes
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Document Summary

Beyond meselsen and stahl"s work, researchers began to question whether dna replicated in the same manner in eukaryotes as it appeared to replicate in prokaryotic bacteria. The complexity and size of the eukaryotic genome made the experiments with labeled isotopes difficult but researchers have since then been able to label individual nucleotides with fluorescent labels. This allowed researchers to examine replication of eukaryotic dna in media containing fluorescent nucleotides and follow entire strands of eukaryotic dna under the microscope. It was found that following rounds of replication of dna and cell division in media containing fluorescent nucleotides, the chromosomes of eukaryotic cells could contain hybrid and fully labelled nucleotides. This leads to observed faintly and darkly fluorescing strands of labeled dna even within one chromosome. These results provided further support for the semiconservative model of dna replication, and indeed it was shown that this mechanism of replication is similar in prokaryotes and eukaryotes.

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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.

Please provide correct answer and explanation to the answer,Thank you!

  1. If an enterprising graduate student decided to repeat theHershey-Chase

    experiment but neglected to perform the blending portion, wherewill the

    isotopes be found?

    a. 35S will be found in the supernatant and 32P will be found inthe pellet

    b. 32P will be found in the supernatant and 35S will be found inthe pellet

    c. Both 32P and 35S will be found in the supernatant

    d. Both 32P and 35S will be found in the pellet

    e. None of the above are correct

  2. Chargaff�s rules include:

    a. The ratio of A�s + T�s to G�s + C�s is always consistent

    b. A=G and T=C

    c. Purines/Pyrimidines = 1

    d. More than one of the above are true

    e. None of the above are true

  3. Sea Urchin DNA contains 18% guanine (which is true); how muchthymine

    does it contain?

    a. 9%

    b. 18%

    c. 32%

    d. 36%

    e. 64%

  4. E. coli DNA contains a little over 25% guanine. If samples weretaken of E.

    coli DNA and Sea Urchin DNA and denatured in water baths, whichwould

    melt at a lower temperature?

    a. E. coli DNA

    b. Sea Urchin DNA

    c. They would melt at the same temperature

    d. There is not enough information to determine the answer

    e. DNA doesn�t �melt,� it isn�t ice cream for goodness sake!

  5. If testing the second generation results in tube B, which modelcan we

    conclude is correct?

    a. Dispersive

    b. Semi-conservative

    c. Conservative

    d. Semi-dispersive

    e. We can�t conclude yet, it could still be more than onepossibility

  6. Phosphorus is required to synthesize dNTPs used in DNAreplication. Imagine

    you grow E. coli in media containing non-radioactive phosphorusfor many

    generations, then switch the E. coli to media containingradioactive

    phosphorous (32P). You then sample the E. coli after one roundof replication

    for radioactivity. Where will you find radioactive phosphorus inthe DNA?

    a. Both strands will contain 32P

    b. One strand will contain 32P

    c. Neither strand will contain 32P

    d. Drats! I knew I should have done suggested problem 12.19!

  7. Which of the following statements about chromosomes are alwaystrue?

    I. Non-histone proteins make up about 5% of a eukaryotic

    chromosome by weight

    II. Histones have a negative charge

    III. Prokaryotes have a single linear chromosome

    a. Only Statement I is true

    b. Only Statement II is true

    c. Only Statement III is true

    d. More than one of the above statements are true

    e. None of the above statements are true

  8. What portion of the human genome is made up of highly repetitiveDNA?

    a. Less than 5%

    b. 6 � 20%

    c. 21 � 30%

    d. 31 � 40%

    e. Over 40%

  9. Which of the following statements are always true?

    I. Histones are very conserved between species

    II. Archaea have nuclei

    III. Prokaryotes are haploid and eukaryotes are diploid

    a. Only Statement I is true

    b. Only Statement II is true

    c. Only Statement III is true

    d. More than one of the above statements are true

    e. None of the above statements are true

  10. An individual�s phenotype is a function of:

    a. The alleles they carry

    b. The environment they live in

    c. The interaction between an individuals genes and theenvironment

    d. Two of the above are correct

    e. All of the above are correct

  11. A homologous pair of chromosomes showing a

    crossover are shown to the right for reference. Are all

    the sperm from one human male genetically identical?

    a. Yes

    b. No, variation occurs during mitosis

    c. No, variation occurs during meiosis I

    d. No, variation occurs during meiosis II

    e. No, variation occurs during both meiosis I and II

  12. Production of gametes in humans requires which kind ofdivision?

    a. Meiotic and is reductional

    b. Mitotic and is reductional

    c. Meiotic and is equational

    d. Mitotic and is equational

    e. None of the above