Question 1

Which enzyme is responsible for relieving the torsional (twisting) stress ahead of the replication fork during DNA replication in prokaryotes?

Accepted Answer

Topoisomerase (DNA gyrase)

Question 2

During DNA replication, why is the lagging strand synthesized discontinuously?

Accepted Answer

Because DNA polymerase can only add nucleotides to the 3' end, requiring synthesis away from the replication fork in short fragments

Question 3

A DNA molecule contains 40% thymine. According to Chargaff's rules, what percentage of guanine does it contain?

Accepted Answer

20%

Question 4

What is the role of single-strand binding proteins (SSBPs) during DNA replication?

Accepted Answer

They prevent re-annealing of separated DNA strands

Question 5

Which of the following best describes the function of telomerase in eukaryotic cells?

Accepted Answer

It adds repetitive DNA sequences to chromosome ends, preventing shortening during replication

Question 6

Which enzyme removes RNA primers and replaces them with DNA during lagging strand synthesis?

Accepted Answer

DNA polymerase I

Question 7

What would happen to a eukaryotic cell that lacks functional telomerase?

Accepted Answer

Its chromosomes would gradually shorten with each cell division

Question 8

Which of the following is NOT a mechanism for correcting base-pairing mistakes in DNA?

Accepted Answer

Transcription

Question 9

A mutation in a gene encoding a DNA repair enzyme is most likely to result in which of the following?

Accepted Answer

Increased risk of cancer

Question 10

Which statement best explains why Okazaki fragments are formed during DNA replication?

Accepted Answer

DNA polymerase can only synthesize DNA in the 5' to 3' direction, so the lagging strand is made in short segments away from the replication fork

Question 11

Which of the following equations correctly represents the direction of DNA synthesis by DNA polymerase III?

Accepted Answer

$$5' \rightarrow 3'$$

Question 12

If a cell is exposed to UV light and develops thymine dimers, which repair mechanism is most likely to fix this damage?

Accepted Answer

Photorepair using photolyase

Question 13

During DNA replication, what provides the free 3'-OH group required for DNA polymerase III to begin synthesis?

Accepted Answer

An RNA primer synthesized by primase

Question 14

Which of the following best describes the semidiscontinuous nature of DNA replication?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously

Question 15

A cell with defective mismatch repair enzymes would most likely:

Accepted Answer

Accumulate more replication errors after DNA synthesis

Question 16

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

Accepted Answer

Ligase

Question 17

In a scenario where a cell accumulates mutations in both DNA repair genes and cell cycle control genes, what is the most likely outcome?

Accepted Answer

The cell may grow uncontrollably, increasing the risk of tumor formation

Question 18

Which of the following is a real-world example of a cell line that expresses telomerase and divides indefinitely?

Accepted Answer

HeLa cells

Question 19

Which of the following best explains why telomeres are composed of repetitive, noncoding DNA sequences?

Accepted Answer

To protect important genes from being lost during chromosome shortening

Question 20

Which of the following steps occurs LAST during lagging strand synthesis?

Accepted Answer

Ligase joins the Okazaki fragments into a continuous strand

DNA Replication and Repair: Synthesis, Chromosome Ends, and Error Correction

Study Guide - Practice Questions