Question 1

Which statement best describes the semiconservative model of DNA replication?

Accepted Answer

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

Question 2

During DNA replication, which enzyme is responsible for unwinding the double helix by breaking hydrogen bonds between base pairs?

Accepted Answer

DNA helicase

Question 3

What is the role of DNA polymerase during DNA replication?

Accepted Answer

It catalyzes the addition of nucleotides to the 3' end of a growing DNA strand.

Question 4

Which of the following best explains why DNA replication is described as 'bidirectional'?

Accepted Answer

Replication proceeds outward in both directions from each origin of replication.

Question 5

Which rule governs the pairing of nucleotides during DNA replication?

Accepted Answer

A pairs with T, G pairs with C

Question 6

A mutation causes DNA polymerase to lose its proofreading ability. What is the most likely consequence?

Accepted Answer

The frequency of replication errors will increase.

Question 7

Which enzyme is responsible for joining Okazaki fragments on the lagging strand during DNA replication?

Accepted Answer

DNA ligase

Question 8

What is the function of primase during DNA replication?

Accepted Answer

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

Question 9

Which of the following best describes the difference between the leading and lagging strands during DNA replication?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments.

Question 10

A cell is exposed to UV radiation, resulting in the formation of thymine dimers. Which repair mechanism is most likely to be activated?

Accepted Answer

Nucleotide excision repair

Question 11

Which equation correctly represents the energy released during the addition of a nucleotide to a growing DNA strand?

Accepted Answer

$$dNTP \rightarrow dNMP + PP_i$$

Question 12

Why is topoisomerase necessary during DNA replication?

Accepted Answer

It relieves torsional stress ahead of the replication fork by creating transient breaks in the DNA.

Question 13

Which of the following is a consequence of depurination in DNA?

Accepted Answer

Loss of a purine base (adenine or guanine) from the DNA backbone

Question 14

A patient has a mutation in the gene encoding telomerase, resulting in reduced enzyme activity. What is the most likely cellular consequence?

Accepted Answer

Chromosomes will become shorter with each cell division.

Question 15

Which process ensures that errors introduced during DNA replication are corrected before cell division?

Accepted Answer

Proofreading by DNA polymerase

Question 16

A single base substitution in the beta-globin gene changes a glutamic acid to valine, resulting in sickle-cell anemia. What type of mutation is this?

Accepted Answer

Missense mutation

Question 17

Which repair mechanism is most likely to result in loss of genetic information when repairing double-strand breaks?

Accepted Answer

Non-homologous end joining

Question 18

During DNA replication, which direction does DNA polymerase synthesize the new strand?

Accepted Answer

5' to 3' direction

Question 19

Which of the following is NOT a function of single-strand binding proteins during DNA replication?

Accepted Answer

Synthesizing RNA primers

Question 20

A cell accumulates a high rate of deamination events. Which base is most likely to be converted, and what is the product?

Accepted Answer

Cytosine to uracil

DNA Replication and Repair: Mechanisms and Key Concepts

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