Comprehension Questions

Section 12.2

Question 12.1

What is semiconservative replication?

Question 12.2

How did Meselson and Stahl demonstrate that replication in E. coli takes place in a semiconservative manner?

Question 12.3

Draw a molecule of DNA undergoing theta replication. On your drawing, identify (a) origin, (b) polarity (5′ and 3′ ends) of all template strands and newly synthesized strands, (c) leading and lagging strands, (d) Okazaki fragments, and (e) location of primers.

Question 12.4

Draw a molecule of DNA undergoing rolling-circle replication. On your drawing, identify (a) origin, (b) polarity (5′ and 3′ ends) of all template and newly synthesized strands, (c) leading and lagging strands, (d) Okazaki fragments, and (e) location of primers.

Question 12.5

Draw a molecule of DNA undergoing eukaryotic linear replication. On your drawing, identify (a) origin, (b) polarity (5′ and 3′ ends) of all template and newly synthesized strands, (c) leading and lagging strands, (d) Okazaki fragments, and (e) location of primers.

Question 12.6

What are three major requirements of replication?

Question 12.7

What substrates are used in the DNA-synthesis reaction?

Section 12.3

Question 12.8

List the different proteins and enzymes taking part in bacterial replication. Give the function of each in the replication process.

Question 12.9

Why is DNA gyrase necessary for replication?

Question 12.10

What similarities and differences exist in the enzymatic activities of DNA polymerases I and III? What is the function of each DNA polymerase in bacterial cells?

Question 12.11

Why is primase required for replication?

Question 12.12

What three mechanisms ensure the accuracy of replication in bacteria?

Section 12.4

Question 12.13

How does replication licensing ensure that DNA is replicated only once at each origin per eukaryotic cell cycle?

Question 12.14

In what ways is eukaryotic replication similar to bacterial replication, and in what ways is it different?

Question 12.15

What is the end-of-chromosome problem for linear replication? Why, in the absence of telomerase, do the ends of chromosomes get progressively shorter each time the DNA is replicated?

Question 12.16

Outline in words and pictures how telomeres at the ends of eukaryotic chromosomes are replicated.

Section 12.5

Question 12.17

Explain how the type of cleavage of the Holliday intermediate leads to noncrossover recombinants and crossover recombinants.

Question 12.18

What are some of the enzymes taking part in recombination in E. coli and what roles do they play?

Question 12.19

What is gene conversion? How does it arise?

For more questions that test your comprehension of the key chapter concepts, go to for this chapter.

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