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 as the DNA helix unwinds?

Accepted Answer

Topoisomerase

Question 3

Why is DNA synthesis considered to be exergonic, even though polymerization should be endergonic?

Accepted Answer

The hydrolysis of the high-energy phosphate bonds in dNTPs releases energy, making the reaction exergonic.

Question 4

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

Accepted Answer

DNA polymerase can only add nucleotides 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 required for DNA polymerase to begin synthesis.

Question 6

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

Accepted Answer

DNA polymerase can only synthesize in the 5' to 3' direction, so it must work 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 enzyme is responsible for joining Okazaki fragments together on the lagging strand?

Accepted Answer

DNA ligase

Question 9

In eukaryotic cells, what problem arises during the replication of linear chromosome ends, and what is the consequence if it is not resolved?

Accepted Answer

The lagging strand cannot be fully replicated, leading to progressive chromosome shortening.

Question 10

Which enzyme solves the end-replication problem in eukaryotic chromosomes, and how does it function?

Accepted Answer

Telomerase; it extends the 3' end of the lagging strand using an RNA template it carries.

Question 11

A researcher observes that a certain cell type can divide indefinitely in culture. Which of the following is most likely true about these cells?

Accepted Answer

They express active telomerase, allowing them to maintain telomere length.

Question 12

Which of the following best describes the proofreading function of DNA polymerase?

Accepted Answer

It removes incorrectly paired nucleotides using its exonuclease activity.

Question 13

If a cell is exposed to UV light, which type of DNA damage is most likely to occur, and what repair mechanism is used to fix it?

Accepted Answer

Formation of thymine dimers; repaired by nucleotide excision repair.

Question 14

During mismatch repair, how does the cell distinguish the newly synthesized DNA strand from the template strand?

Accepted Answer

The newly synthesized strand is not yet methylated, allowing repair enzymes to identify and correct errors.

Question 15

Which of the following equations correctly represents the directionality of DNA synthesis?

Accepted Answer

$$5' \rightarrow 3'$$

Question 16

A patient is diagnosed with a genetic disorder that results in rapid aging due to shortened chromosomes. Which enzyme is most likely defective in this patient?

Accepted Answer

Telomerase

Question 17

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

Accepted Answer

Synthesizing ribosomal RNA for protein synthesis.

Question 18

Which protein is responsible for breaking hydrogen bonds between DNA strands to open the double helix during replication?

Accepted Answer

Helicase

Question 19

A scientist is studying a bacterial cell with a mutation that prevents the formation of a replication bubble. Which process is most directly affected?

Accepted Answer

Initiation of DNA replication at the origin of replication.

Question 20

Which of the following best explains why most somatic cells have a limited number of divisions?

Accepted Answer

Their telomeres shorten with each division, eventually triggering cell division to stop.

DNA and the Gene: Synthesis and Repair – Study Notes

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