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Molecular Biology

Robert F. Weaver

Chapter 22

Homologous Recombination - all with Video Answers

Educators

Chapter Questions

01:11

Problem 1

List the three steps in homologous recombination in which RecA participates, with a short explanation of each.

Jennifer Stoner
Jennifer Stoner
Numerade Educator
06:18

Problem 1

Draw a diagram of a Holliday junction. Starting with that diagram, illustrate:
a. Branch migration to the right, then resolution to yield a short heteroduplex, or resolution to yield crossover recombinant DNAs
b. Branch migration to the left, then resolution to yield a short heteroduplex, or resolution to yield crossover recombinant DNAs

Rabeya Zahid
Rabeya Zahid
Numerade Educator

Problem 2

What evidence indicates that RecA coats single-stranded DNA? What role does SSB play in the interaction between RecA and single-stranded DNA?

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01:06

Problem 2

Describe or diagram the products of RecBCD pathway recombination in E. coli cells with mutations in the following genes:
a. $\operatorname{rec} B$
b. $\operatorname{rec} A$
c. ruvA
d. ruv $B$
c. $r u v \mathrm{C}$

Josee Pacheco
Josee Pacheco
Numerade Educator

Problem 3

Describe and give the results of an experiment that shows that $\operatorname{RecA}$ is required for synapsis at the beginning of recombination.

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00:27

Problem 3

Show how you could use DNase footprinting to demonstrate that RuvA binds to the center of the Holliday junction, and that RuvB binds to the upstream side relative to the direction of branch migration.

Josee Pacheco
Josee Pacheco
Numerade Educator
02:44

Problem 4

How would you show that the apparent synapsis you observe by electron microscopy is really synapsis, rather than true base pairing?

Rabeya Zahid
Rabeya Zahid
Numerade Educator
03:10

Problem 4

What would be the final mixture of alleles in the gene conversion depicted in Figure 22.24 if both heteroduplexes were converted to $A / A$ by mismatch repair? What if one heteroduplex were converted to $A / A$ and the other to $a / a$ ?

Mathew Botros
Mathew Botros
Montclair State University
02:44

Problem 5

One of the two elements intimately involved in the process of strand exchange is the Chi sites on the DNA. It is believed that Chi sites stimulate the RecBCD pathway but not several other homologous pathways ( $\lambda$ Red, E.coli RecE and RecF). Describe an experiment that would test this hypothesis.

Rabeya Zahid
Rabeya Zahid
Numerade Educator

Problem 5

Describe and give the results of an experiment that shows that RecBCD nicks DNA near a Chi site. How could you demonstrate that it is $\mathrm{RecBCD}$, and not a contaminant, that causes the nicking?

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Problem 6

Show how you could use a gel mobility shift assay to demonstrate that RuvA can bind to a Holliday junction by itself at high concentration, that RuvB cannot bind by itself at all, and that RuvA and RuvB can bind cooperatively at relatively low concentrations. What is the function of glutaraldehyde in this experiment?

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06:18

Problem 7

Draw a diagram of the RuvAB-Holliday junction complex, with the Holliday junction in its familiar cross-shaped form, ready for branch migration. Include the RuvB rings, but not the RuvA tetramer.

Rabeya Zahid
Rabeya Zahid
Numerade Educator

Problem 8

Describe and give the results of an experiment that shows that RuvC can resolve a Holliday junction.

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Problem 9

What evidence suggests that RuvA, B, and C are all together in a complex with a Holliday junction?

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02:25

Problem 10

Present a model for meiotic recombination in yeast.

Jessica Wooten
Jessica Wooten
Numerade Educator

Problem 11

Describe and give the results of an experiment that shows that a DSB forms during meiotic recombination in yeast.

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Problem 12

Describe and give the results of an experiment that shows that Spo11 is covalently attached to a DSB during meiotic recombination in yeast.

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Problem 13

Describe and give the results of an experiment that demonstrates the formation of Spo11-linked oligonucleotides of two size classes.

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02:44

Problem 14

What do the two size classes of Spo11-linked oligonucleotides, and the timing of their appearance and disappearance, suggest about the mechanism of homologous recombination in yeast? Illustrate your answer with a drawing.

Rabeya Zahid
Rabeya Zahid
Numerade Educator
00:31

Problem 15

Present a model for meiotic gene conversion.

Jennifer Stoner
Jennifer Stoner
Numerade Educator