Question 1

Which of the following best describes the role of licensing factors in eukaryotic DNA replication?

Accepted Answer

They recruit inactive origins to form the pre-replication complex (Pre-RC).

Question 2

A temperature-sensitive mutant in a bacterial DNA polymerase shows normal growth at 30°C but fails to replicate DNA at 42°C. What is the most likely explanation for this phenotype?

Accepted Answer

The mutant protein is functional at 30°C but loses its proper conformation and function at 42°C.

Question 3

Which stage of eukaryotic DNA replication is blocked when licensing factors are removed from the nucleus and degraded?

Accepted Answer

Initiation

Question 4

What is the primary function of the MCM helicase during DNA replication?

Accepted Answer

Unwinding the DNA duplex using ATP hydrolysis

Question 5

Which of the following statements about Okazaki fragments is TRUE?

Accepted Answer

They are short DNA fragments synthesized discontinuously on the lagging strand.

Question 6

A mutation in a gene encoding a protein exclusively involved in the initiation stage of DNA replication would most likely result in which phenotype?

Accepted Answer

Cell growth stops immediately upon temperature shift.

Question 7

Which enzymatic activity is shared by all DNA polymerases during DNA synthesis?

Accepted Answer

Formation of phosphodiester bonds between the 3'-OH of one nucleotide and the 5'-phosphate of the next nucleotide: $$\mathrm{3'-OH + 5'-P \rightarrow phosphodiester\ bond}$$

Question 8

Which property of high-fidelity DNA polymerases helps prevent replication errors?

Accepted Answer

A tightly fitted active site that only allows Watson-Crick base pairs to fit

Question 9

What is the consequence of the end-replication problem in linear chromosomes?

Accepted Answer

Chromosomes shorten with each cell division due to incomplete replication of the ends.

Question 10

Which enzyme solves the end-replication problem in eukaryotic cells?

Accepted Answer

Telomerase

Question 11

A student observes that a DNA polymerase mutant has reduced processivity. Which structural feature is most likely defective?

Accepted Answer

The clamp loader or clamp subunit that holds the polymerase on the DNA

Question 12

Which of the following best explains why DNA polymerases require an RNA primer to begin synthesis?

Accepted Answer

DNA polymerases can only add nucleotides to an existing 3'-OH group.

Question 13

Which of the following is a function of DNA ligase during replication?

Accepted Answer

Joining Okazaki fragments by forming phosphodiester bonds

Question 14

What is the main difference between leading and lagging strand synthesis during DNA replication?

Accepted Answer

Leading strand is synthesized continuously, lagging strand is synthesized discontinuously as Okazaki fragments.

Question 15

Which of the following DNA polymerase activities is responsible for proofreading?

Accepted Answer

3' to 5' exonuclease activity

Question 16

A mutation in a protein involved in elongation of DNA replication would most likely result in which phenotype?

Accepted Answer

Cell growth stops slowly as incomplete replication accumulates.

Question 17

Which of the following best describes the structure of telomeric DNA?

Accepted Answer

Tandemly repeated sequences that can form T-loops

Question 18

What is the function of the RNA component in the telomerase enzyme?

Accepted Answer

It acts as a template for the addition of telomeric repeats to the 3' end of DNA.

Question 19

Which of the following is a consequence of defective single-strand binding protein (SSB) during DNA replication?

Accepted Answer

Reformation of the DNA duplex at the replication fork, hindering replication

DNA Replication II: Mechanisms, Regulation, and Mutational Analysis

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