Question 1

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

Accepted Answer

DNA stores the instructions for making proteins and regulates cellular activities.

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 crucial for DNA replication?

Accepted Answer

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

Question 7

What did Griffith’s experiment demonstrate?

Accepted Answer

Genetic information can be transferred between organisms, transforming their phenotype.

Question 8

What is meant by 'semiconservative replication'?

Accepted Answer

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

Question 9

Which enzyme relieves the strain ahead of the replication fork during DNA replication?

Accepted Answer

Topoisomerase

Question 10

Why is the lagging strand synthesized discontinuously?

Accepted Answer

The lagging strand template is oriented 5’ to 3’ away from the replication fork, requiring synthesis in short fragments.

Question 11

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

Accepted Answer

DNA polymerase I

Question 12

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

Accepted Answer

By proofreading and replacing incorrectly paired bases

Question 13

Which of the following best describes the difference between DNA replication in cells and PCR in the laboratory?

Accepted Answer

DNA replication copies the entire genome; PCR amplifies a specific DNA region.

Question 14

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

Accepted Answer

23%

Question 15

Which of the following is a common application of PCR in real-world science?

Accepted Answer

Amplifying DNA for crime scene analysis

Question 16

Which of the following correctly matches the enzyme to its function during DNA replication?

Accepted Answer

DNA ligase: joins Okazaki fragments together

Question 17

If a mutation prevents the formation of hydrogen bonds between bases, which process would be directly affected?

Accepted Answer

Base pairing between complementary DNA strands

Question 18

Which of the following best explains why multiple origins of replication are necessary in human chromosomes?

Accepted Answer

Human chromosomes are large and linear, requiring multiple starting points for efficient replication.

Question 19

Which of the following is the correct sequence of events during DNA replication?

Accepted Answer

DNA helicase unwinds DNA → Primase synthesizes primers → DNA polymerase III synthesizes new DNA

Question 20

Which of the following equations correctly represents the condensation reaction that forms a phosphodiester bond?

Accepted Answer

$$	ext{Nucleotide}_1 + 	ext{Nucleotide}_2 ightarrow 	ext{Nucleotide}_1-	ext{Nucleotide}_2 + H_2O$$

DNA Replication: Structure, Function, and Mechanisms

Study Guide - Practice Questions