Question 1

Which activity of DNA polymerase I is responsible for removing RNA primers during DNA replication in E. coli?

Accepted Answer

Its 5'-3' exonuclease activity

Question 2

After DNA polymerase I removes the RNA primer on the lagging strand, what is the next step in Okazaki fragment maturation?

Accepted Answer

DNA polymerase I fills the gap with DNA nucleotides

Question 3

What is the role of DNA ligase in the process of Okazaki fragment ligation?

Accepted Answer

It catalyzes the formation of a phosphodiester bond to join DNA fragments

Question 4

A mutation in E. coli results in a DNA polymerase I that lacks 5'-3' exonuclease activity but retains all other functions. What is the most likely consequence during DNA replication?

Accepted Answer

RNA primers will not be removed from Okazaki fragments

Question 5

Which of the following best describes the directionality of DNA polymerase I's exonuclease activity that removes RNA primers?

Accepted Answer

$$5' 	o 3'$$

Question 6

During lagging strand synthesis, which enzyme is responsible for sealing the final 'nick' between adjacent Okazaki fragments after primer removal and gap filling?

Accepted Answer

DNA ligase

Question 7

If DNA ligase is nonfunctional in a bacterial cell, what would be the most direct effect on DNA replication?

Accepted Answer

Okazaki fragments would remain unjoined, resulting in fragmented DNA

Question 8

Which of the following sequences of events correctly describes the order of enzymatic activities during the maturation of Okazaki fragments?

Accepted Answer

DNA polymerase I removes the primer, DNA polymerase I fills the gap, DNA ligase seals the nick

Question 9

A researcher observes that after DNA replication, short stretches of RNA remain at the 5' ends of Okazaki fragments. Which enzyme is most likely defective?

Accepted Answer

DNA polymerase I

Question 10

Which of the following best explains why DNA ligase is necessary after DNA polymerase I has filled in the gap left by primer removal?

Accepted Answer

DNA polymerase I cannot form the final phosphodiester bond between adjacent DNA fragments

Question 11

In a mutant E. coli strain, Okazaki fragments accumulate but are not joined into a continuous DNA strand. Which enzyme is most likely nonfunctional?

Accepted Answer

DNA ligase

Question 12

Which of the following is NOT a function of DNA polymerase I in E. coli?

Accepted Answer

Sealing the final phosphodiester bond between Okazaki fragments

Question 13

A patient has a genetic disorder affecting DNA ligase. Which of the following cellular processes would be most directly impaired?

Accepted Answer

Joining of Okazaki fragments during DNA replication

Question 14

Which of the following best describes the role of the 5'-3' polymerase activity of DNA polymerase I during Okazaki fragment processing?

Accepted Answer

It adds DNA nucleotides to fill the gap after RNA primer removal

Question 15

Suppose a new antibiotic specifically inhibits the 5'-3' exonuclease activity of DNA polymerase I. What would be the most likely effect on bacterial DNA replication?

Accepted Answer

RNA primers would persist, preventing proper DNA synthesis

DNA Replication: Enzymes, Mechanisms, and Molecular Analysis

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