Question 1

Which of the following best describes the general function of DNA in a cell?

Accepted Answer

DNA provides the instructions for making proteins and must be copied before cell division.

Question 2

Which components form a nucleotide in DNA?

Accepted Answer

A phosphate group, a deoxyribose sugar, and a nitrogenous base

Question 3

Which bonds connect the sugar-phosphate backbone of DNA, and which bonds connect the nitrogenous bases?

Accepted Answer

Phosphodiester bonds connect the backbone; hydrogen bonds connect the bases.

Question 4

Given the DNA sequence 5'-A G T T C A G C T-3', what is the complementary strand?

Accepted Answer

3'-T C A A G T C G A-5'

Question 5

What functional group is found at the 5’ end of a DNA strand, and what is found at the 3’ end?

Accepted Answer

5’ end: phosphate group; 3’ end: hydroxyl group

Question 6

Why is the 3’ end of a DNA strand important during DNA replication?

Accepted Answer

New nucleotides can only be added to the 3’ end due to the presence of a hydroxyl group.

Question 7

In Griffith’s experiment, what was the key finding regarding the transfer of genetic material?

Accepted Answer

Hereditary material from dead S strain bacteria transformed R strain bacteria into a virulent form.

Question 8

What did the Avery-MacLeod-McCarty experiment demonstrate about the hereditary molecule?

Accepted Answer

DNA is the molecule responsible for heredity.

Question 9

What is meant by 'semiconservative replication'?

Accepted Answer

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

Question 10

Which enzyme is responsible for relieving strain ahead of the replication fork during DNA replication?

Accepted Answer

Topoisomerase

Question 11

Why is the leading strand synthesized continuously while the lagging strand is synthesized in fragments?

Accepted Answer

The leading strand template is oriented 3’ to 5’ toward the fork, allowing continuous synthesis; the lagging strand template is oriented 5’ to 3’, requiring discontinuous synthesis.

Question 12

Which enzyme removes RNA primers and fills in the gaps with DNA nucleotides during replication?

Accepted Answer

DNA polymerase I

Question 13

What is the role of DNA ligase in DNA replication?

Accepted Answer

It forms phosphodiester bonds between Okazaki fragments on the lagging strand.

Question 14

Which of the following best describes the function of DNA polymerase III during replication?

Accepted Answer

It synthesizes new DNA strands by adding nucleotides to the 3’ end of a primer.

Question 15

How does DNA polymerase III ensure the accuracy of DNA replication?

Accepted Answer

It proofreads and removes incorrectly paired nucleotides during synthesis.

Question 16

Which of the following is a key difference between DNA replication in cells and PCR in the laboratory?

Accepted Answer

DNA replication uses helicase to separate strands, while PCR uses heat.

Question 17

A DNA sample is found to contain 27% adenine. According to Chargaff’s rule, what percentage of guanine is present?

Accepted Answer

$$100\% - (27\% + 27\%) = 46\%$$; $$46\% / 2 = 23\%$$ guanine

Question 18

Which of the following is NOT a required ingredient for a PCR reaction?

Accepted Answer

RNA polymerase

Question 19

Which real-world application relies on the use of PCR?

Accepted Answer

Crime scene DNA analysis

Question 20

A mutation occurs during DNA replication, but the error is not corrected by DNA polymerase III. Which enzyme can remove a large chunk of incorrectly copied DNA for repair?

Accepted Answer

Nucleotide excision enzymes

DNA Replication: Structure, Function, and Mechanisms

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