Question 1

Which of the following best describes the semiconservative model of DNA replication?

Accepted Answer

Each daughter DNA molecule consists of one old strand and one newly synthesized strand.

Question 2

During DNA replication, which enzyme is responsible for relieving the tension created ahead of the replication fork due to unwinding of the double helix?

Accepted Answer

Topoisomerase

Question 3

Why is DNA synthesis considered to be exergonic, even though the formation of phosphodiester bonds is endergonic?

Accepted Answer

The hydrolysis of the two extra phosphates from dNTPs releases enough energy to drive the reaction.

Question 4

Which of the following statements about the directionality of DNA synthesis is correct?

Accepted Answer

DNA polymerase adds nucleotides only to the 3' end of a growing DNA strand.

Question 5

A mutation in the gene encoding primase would most directly affect which aspect of DNA replication?

Accepted Answer

The ability to synthesize RNA primers needed to initiate DNA synthesis.

Question 6

Which of the following best explains why the lagging strand is synthesized discontinuously?

Accepted Answer

DNA polymerase can only synthesize DNA in the 5' to 3' direction, away from the replication fork on the lagging strand.

Question 7

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

Accepted Answer

To prevent separated DNA strands from re-annealing.

Question 8

Which of the following is a direct consequence of the end-replication problem in eukaryotic cells?

Accepted Answer

Chromosomes become progressively shorter with each cell division.

Question 9

Telomerase is most active in which type of cells?

Accepted Answer

Gametes and stem cells

Question 10

A scientist observes that a certain cell line can divide indefinitely in culture. Which of the following is the most likely explanation?

Accepted Answer

The cells express active telomerase, maintaining telomere length.

Question 11

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

Accepted Answer

It joins Okazaki fragments on the lagging strand by forming phosphodiester bonds.

Question 12

A patient is exposed to high levels of UV radiation, resulting in the formation of thymine dimers in their DNA. Which DNA repair mechanism is primarily responsible for correcting this damage?

Accepted Answer

Nucleotide excision repair

Question 13

Which of the following equations correctly represents the hydrolysis of a deoxyribonucleoside triphosphate (dNTP) during DNA synthesis?

Accepted Answer

$$\mathrm{dNTP} \rightarrow \mathrm{dNMP} + 2\mathrm{P_i}$$

Question 14

If a mutation prevents DNA polymerase from proofreading, what is the most likely consequence?

Accepted Answer

The mutation rate during DNA replication would increase.

Question 15

Which of the following is NOT a function of the replisome during DNA replication?

Accepted Answer

Synthesizing ribosomal RNA for protein synthesis

Question 16

A cell is found to have a high rate of mismatched base pairs after DNA replication. Which repair mechanism is most likely defective in this cell?

Accepted Answer

Mismatch repair

Question 17

Which of the following best explains why telomeres do not contain genes?

Accepted Answer

Their primary function is to protect coding DNA from being lost during replication.

Question 18

Which of the following scenarios would most likely result in cancer cell immortality?

Accepted Answer

Activation of telomerase in somatic cells

Question 19

A researcher is studying a bacterial mutant that cannot synthesize Okazaki fragments. Which protein is most likely nonfunctional in this mutant?

Accepted Answer

Primase

Question 20

Which of the following steps occurs LAST during the repair of UV-induced thymine dimers?

Accepted Answer

DNA ligase seals the repaired DNA strand.

DNA and the Gene: Synthesis and Repair – Study Notes

Study Guide - Practice Questions

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