Molecular Biology

Robert F. Weaver

Chapter 20 DNA Replication, Damage, and Repair - all with Video Answers

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Chapter Questions

01:42

Problem 1

Compare and contrast the conservative, semiconservative, and dispersive mechanisms of DNA replication.

Mikayla Stephens

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02:49

Problem 1

Why is it improbable that we will ever observe continuous DNA replication of both strands in nature?

Mikayla Stephens

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02:29

Problem 2

Describe and give the results of an experiment that shows that DNA replication is semiconservative.

Ritika Shakkerwal

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Problem 2

You are studying a protein that you suspect has DNA helicase activity. Describe how you would assay the protein for this activity and show sample positive results.

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01:39

Problem 3

Compare and contrast the continuous, discontinuous, and semidiscontinuous modes of DNA replication.

Jessica Wooten

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01:42

Problem 3

You are studying a protein that you suspect has DNA topoisomerase activity. Describe how you would assay the protein for the activity and show sample positive results.

Madi Sousa

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01:39

Problem 4

Describe and give the results of an experiment that shows that DNA replication is at least semidiscontinuous.

Jessica Wooten

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02:21

Problem 4

Explain the difference between DNA damage and mutation. How do mutations in E. coli DNA polymerase V illustrate this difference?

Aadit Sharma

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01:58

Recently, as a post-doc in a highly reputable laboratory, you designed a new single-celled organism only capable of three DNA repair mechanisms. You have been asked to present your research at a prestigious Molecular Biology conference Describe how you will support your reason for choosing the three repair mechanisms and discuss if there are overlaps or gaps between the chosen mechanisms. Additionally, explain the types of mutations your cell can overcome and the types of damage that may potentially destroy your new organism. You may assume that your organism already has a homologous recombination system.

Anna Miller

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01:39

Problem 5

What is the evidence for fully discontinuous DNA replication in E. coli cells?

Jessica Wooten

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Problem 6

Describe and give the results of an experiment that measures the size of the primers on Okazaki fragments.

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05:46

Problem 7

Present electron microscopic evidence that DNA replication of the B. subtilis chromosome is bidirectional, whereas replication of the colE1 plasmid is unidirectional.

Rashmi Sinha

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04:04

Problem 8

Diagram the rolling circle replication mechanism used by the $\lambda$ phage.

Jessica Wooten

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01:00

Problem 9

Diagram the proofreading process used by E. coli DNA polymerases.

Wade Corn

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04:55

Problem 10

What activities are contained in E. coli DNA polymerase I? What is the role of each in DNA replication?

Jessica Wooten

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03:05

Problem 11

How does the Klenow fragment differ from the intact E. coli DNA polymerase I? Which enzyme would you use in nick translation? DNA end-filling? Why?

Shiksha Dutta

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02:03

Problem 12

Of the three DNA polymerases in E. coli, which is essential for DNA replication? Present evidence.

Jessica Wooten

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08:37

Problem 13

Which pol III core subunit has the DNA polymerase activity? How do we know?

Susan Hallstrom

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01:00

Problem 14

Which pol III core subunit has the proofreading activity? How do we know?

Wade Corn

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02:25

Problem 15

Explain how the necessity for proofreading rationalizes the existence of priming in DNA replication.

Parvati Devi

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01:58

Problem 16

List the eukaryotic DNA polymerases and their roles. Outline evidence for these roles.

Jessica Wooten

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01:25

Problem 17

Compare and contrast the activity of a helicase with that of a topoisomerase in the context of DNA replication.

Katie Haasch

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02:10

Problem 18

What roles do SSBs play in DNA replication?

Dennis Howard

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01:32

Problem 19

Explain why nicking one strand of a supercoiled DNA removes the supercoiling.

Jennifer Stoner

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02:32

Problem 20

How do we know that DNA gyrase forms a covalent bond between an enzyme tyrosine and DNA? What is the advantage of forming this bond?

Shiksha Dutta

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05:43

Problem 21

Present a model, based on the structure of yeast DNA topoisomerase II, for the DNA segment-passing step.

Jennifer Stoner

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01:24

Problem 22

Compare and contrast the DNA damage done by UV rays and $x$-rays or gamma rays.

Grant Castaneda

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Problem 23

What two enzymes catalyze direct reversal of DNA damage? Diagram the mechanisms they use.

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05:17

Problem 24

Compare and contrast base excision repair and nucleotide excision repair. Diagram both processes. For what types of damage is each primarily responsible?

Syed Anas

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00:26

Problem 25

What enzyme performs proofreading in human base excision repair? Outline the evidence supporting your answer.

Mishal Gul

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05:43

Problem 26

Briefly describe the crystal structures of complexes between the human oxoG repair enzyme (hOGG1) and an oxoG-C pair, or a normal G-C pair. How do these structures explain why oxoG is removed, while ordinary $\mathrm{G}$ is not.

Niamat Khuda

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Problem 27

How does transcription-coupled NER differ from global genome NER?

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01:03

Problem 28

Outline the nonhomologous end-joining mechanism mammals use to repair double-stand DNA breaks. Show how this process can lead to loss of nucleotides at the repair site.

Mikayla Stephens

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06:08

Problem 29

What DNA repair system is missing in most cases of xeroderma pigmentosum? Why does that make XP patients so sensitive to UV light? What is the primary backup system for these patients?

Sana Riaz

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06:08

Problem 30

What DNA repair system is missing in XP-V patients? Why is the incidence of skin cancer lower in these people than in typical XP patients? What is the backup system for lesions missed by the NER system in XP-V patients?

Sana Riaz

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00:34

Problem 31

Why is chromatin remodeling needed for double-strand break repair in eukaryotes?

Josee Pacheco

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Problem 32

Diagram the mismatch repair mechanism in E. coli.

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Problem 33

Diagram the recombination repair mechanism in E. coli.

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00:36

Problem 34

Diagram the error-prone bypass system in E. coli.

Carlene Jimenez

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01:58

Problem 35

Explain why recombination repair and error-prone bypass are not real repair systems.

Anna Miller

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02:13

Problem 36

Present evidence that shows that DNA polymerase $\eta$ can bypass a thymine dimer and an AP site but not a (6-4) photoproduct, and that DNA polymerase $\alpha$ cannot bypass any of these lesions.

Aadit Sharma

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