Question 1

Which enzyme is responsible for unwinding the DNA double helix at the origin of replication during DNA replication?

Accepted Answer

Helicase

Question 2

What is the primary function of single-stranded binding proteins (SSBs) during DNA replication?

Accepted Answer

They prevent the separated DNA strands from re-annealing.

Question 3

Which of the following statements correctly describes the direction in which DNA polymerase synthesizes new DNA?

Accepted Answer

DNA polymerase synthesizes DNA in the 5' → 3' direction.

Question 4

During DNA replication, what is the role of topoisomerase II?

Accepted Answer

It introduces double-stranded breaks to relieve supercoiling ahead of the replication fork.

Question 5

In prokaryotic DNA replication, what is the name of the short RNA sequence that allows DNA polymerase to begin synthesis?

Accepted Answer

RNA primer

Question 6

Which of the following best explains why DNA replication is considered semiconservative?

Accepted Answer

Each new DNA molecule contains one parental strand and one newly synthesized strand.

Question 7

A mutation in the gene encoding DNA helicase would most likely result in which of the following cellular outcomes?

Accepted Answer

Inability to separate the two DNA strands, halting replication

Question 8

Which of the following equations correctly represents the formation of a phosphodiester bond during DNA polymerization?

Accepted Answer

$dNTP + (DNA)_{n} \rightarrow (DNA)_{n+1} + PP_i$

Question 9

Why are origins of replication typically rich in A-T base pairs?

Accepted Answer

A-T base pairs form only two hydrogen bonds, making them easier to separate.

Question 10

Which statement best describes the difference between prokaryotic and eukaryotic DNA replication origins?

Accepted Answer

Eukaryotes have multiple origins of replication per chromosome, while prokaryotes typically have one.

Question 11

During DNA replication, the lagging strand is synthesized in short fragments known as:

Accepted Answer

Okazaki fragments

Question 12

Which enzyme is responsible for joining Okazaki fragments together on the lagging strand?

Accepted Answer

DNA ligase

Question 13

A patient is found to have a defect in topoisomerase I. What is the most likely consequence for DNA replication in their cells?

Accepted Answer

Accumulation of supercoiling ahead of the replication fork

Question 14

Which of the following best describes the function of primase during DNA replication?

Accepted Answer

It synthesizes short RNA primers to provide a starting point for DNA polymerase.

Question 15

If DNA polymerase could synthesize DNA in the 3' → 5' direction, which of the following consequences would most likely occur?

Accepted Answer

Proofreading would be less efficient, increasing mutation rates.

Question 16

Which of the following is a correct description of the antiparallel nature of DNA replication?

Accepted Answer

One new strand is synthesized continuously, while the other is synthesized discontinuously.

Question 17

A researcher adds a chemical that specifically inhibits DNA ligase activity in a eukaryotic cell. Which of the following would you expect to observe?

Accepted Answer

Accumulation of unjoined Okazaki fragments on the lagging strand

Question 18

Which of the following best explains why DNA polymerase requires an RNA primer to initiate synthesis?

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3' hydroxyl group.

Question 19

Which of the following is the correct order of events during DNA replication at a replication fork?

Accepted Answer

Helicase unwinds DNA → SSBs bind → Primase synthesizes RNA primer → DNA polymerase extends DNA

DNA Replication: Mechanisms and Enzymes

Study Guide - Practice Questions