Question 1

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

Accepted Answer

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

Question 2

During DNA replication, which enzyme is responsible for relieving the tension created ahead of the replication fork?

Accepted Answer

Topoisomerase

Question 3

Why is DNA synthesis considered to be an exergonic process?

Accepted Answer

The formation of phosphodiester bonds releases energy stored in dNTPs.

Question 4

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

Accepted Answer

DNA polymerase synthesizes DNA in the $$5' \rightarrow 3'$$ direction.

Question 5

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 6

Which enzyme synthesizes the short RNA primer required for DNA polymerase to begin synthesis?

Accepted Answer

Primase

Question 7

Why is the lagging strand synthesized discontinuously during DNA replication?

Accepted Answer

DNA polymerase cannot synthesize DNA in the $$3' \rightarrow 5'$$ direction.

Question 8

What are Okazaki fragments?

Accepted Answer

Short segments of DNA synthesized on the lagging strand

Question 9

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

Accepted Answer

DNA ligase

Question 10

What is the main problem encountered during the replication of the ends of linear chromosomes (telomeres)?

Accepted Answer

DNA polymerase cannot add nucleotides to the $$3'$$ end without a primer.

Question 11

How does telomerase prevent the shortening of chromosomes during DNA replication?

Accepted Answer

By using an RNA template to extend the $$3'$$ end of the lagging strand

Question 12

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

Accepted Answer

They lack telomerase, so their telomeres shorten with each division.

Question 13

Cancer cells often have active telomerase. What is a likely consequence of this?

Accepted Answer

Cancer cells can divide indefinitely.

Question 14

Which of the following mechanisms is responsible for correcting mismatched bases immediately after DNA synthesis?

Accepted Answer

Mismatch repair

Question 15

What is the role of DNA polymerase's exonuclease activity during replication?

Accepted Answer

To remove incorrectly paired nucleotides

Question 16

Exposure to UV light can cause thymine dimers in DNA. What is the consequence of these dimers if not repaired?

Accepted Answer

They block DNA replication by creating kinks in the DNA strand.

Question 17

Which DNA repair system recognizes and removes thymine dimers caused by UV light?

Accepted Answer

Nucleotide excision repair

Question 18

A scientist observes that a bacterial cell is unable to synthesize new DNA strands. Which protein is most likely defective?

Accepted Answer

DNA polymerase

Question 19

If a mutation prevents the production of primase in a cell, what would be the immediate effect on DNA replication?

Accepted Answer

RNA primers would not be synthesized, preventing DNA polymerase from starting replication.

Question 20

Which of the following best explains why DNA polymerase requires a primer to begin synthesis?

Accepted Answer

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

DNA and the Gene: Synthesis and Repair – Study Notes

Study Guide - Practice Questions