Question 1

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

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3' hydroxyl group provided by the primer.

Question 2

A DNA molecule is analyzed and found to contain 30% guanine. According to Chargaff’s rules, what percentage of adenine would you expect to find in this DNA?

Accepted Answer

$20\%$

Question 3

Which enzyme is responsible for relieving the strain caused by tight twisting ahead of the replication fork during DNA replication?

Accepted Answer

Topoisomerase

Question 4

During DNA replication in bacteria, which enzyme replaces RNA primers with DNA nucleotides?

Accepted Answer

DNA Polymerase I

Question 5

A mutation occurs that disables the function of DNA ligase in a bacterial cell. Which of the following would most likely result?

Accepted Answer

Okazaki fragments on the lagging strand would remain unjoined.

Question 6

Which of the following best describes the difference between purines and pyrimidines in DNA?

Accepted Answer

Purines have two rings, while pyrimidines have one ring.

Question 7

Which of the following is a direct result of a mutation that escapes proofreading and repair during DNA replication?

Accepted Answer

A permanent change in the DNA sequence that can be inherited by future generations.

Question 8

A scientist is studying a eukaryotic chromosome and observes DNA wrapped around protein spools. What is the name of this structural unit?

Accepted Answer

Nucleosome

Question 9

Which of the following best explains why the lagging strand is synthesized in short fragments during DNA replication?

Accepted Answer

DNA polymerase can only synthesize DNA in the 5' to 3' direction, requiring discontinuous synthesis on the lagging strand.

Question 10

If a DNA double helix is composed of 18% cytosine, what is the percentage of guanine present?

Accepted Answer

$18\%$

Question 11

Which of the following processes is responsible for correcting errors in base pairing that escape the proofreading activity of DNA polymerase?

Accepted Answer

Mismatch repair

Question 12

A patient is exposed to a chemical that causes thymine dimers to form in their DNA. Which repair mechanism is most likely to fix this damage?

Accepted Answer

Nucleotide excision repair

Question 13

Which of the following best describes the role of single-stranded binding proteins during DNA replication?

Accepted Answer

They stabilize unwound DNA strands and prevent them from re-annealing.

Question 14

A researcher discovers a new organism with DNA composed of 22% thymine. What is the expected percentage of guanine in this organism’s DNA?

Accepted Answer

$28\%$

Question 15

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

Accepted Answer

Unwinding the DNA double helix

Question 16

Which of the following best explains why mutations are important for evolution?

Accepted Answer

They introduce genetic variation, which is essential for natural selection to act upon.

Question 17

A DNA sample is found to have 27% adenine. What is the expected percentage of cytosine in this sample?

Accepted Answer

$23\%$

Question 18

Which of the following best describes the structure of a nucleosome?

Accepted Answer

A segment of DNA wrapped around a core of histone proteins

Question 19

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

Accepted Answer

5' to 3' direction

Question 20

Which of the following historical discoveries provided direct evidence for the helical structure of DNA?

Accepted Answer

X-ray crystallography images produced by Rosalind Franklin

The Molecular Basis of Inheritance: Structure and Replication of DNA

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