A R I Z O N A S TAT E U N I V E R S I T Y · S C H O O L O F L I F E S C I E N C E S
ASU BIO 181 Exam 2 (modules
7-12)
Practice Question Bank
Comprehensive Review with 76 Questions, Answers & Rationales
BIO 181 — General Biology I
Edition 1 · August 2026
,Table of Contents
1. Instructions for Use 2
2. Practice Questions with Answers & Rationales 2
BIO 181 · Arizona State University Page 1
, ASU BIO 181 EXAM 2 (MODULES 7-12) PRACTICE GUIDE METABOLISM, IMMUNOLOGY & GENETICS
How to Use This Guide
Read each stem, choose your answer, then check the rationale below. The correct option is marked, and each wrong option
is explained. This guide contains 76 questions covering the full scope of the ASU BIO 181 Exam 2 (modules 7-12).
Category: ASU BIO 181 — Exam 2 (modules 7-12)
1 Which enzyme unwraps the double helix?
A Helicase
B Primase
C DNA Polymerase III
D Ligase
Why A is correct: Helicase unwinds the double helix by breaking hydrogen bonds between base pairs during DNA
replication.
B — Primase synthesizes RNA primers.
C — DNA Polymerase III synthesizes new DNA.
D — Ligase joins Okazaki fragments.
2 Which enzyme is used first to permit DNA polymerase III to begin replicating the 3' strand?
A Primase
B Helicase
C Ligase
D Topoisomerase
Why A is correct: Primase synthesizes an RNA primer, which is required for DNA Polymerase III to begin replication.
B — Helicase unwinds DNA but does not synthesize primers.
C — Ligase joins fragments after replication.
D — Topoisomerase relieves supercoiling.
ASU BIO 181 Exam 2 (modules
7-12)
Practice Question Bank
Comprehensive Review with 76 Questions, Answers & Rationales
BIO 181 — General Biology I
Edition 1 · August 2026
,Table of Contents
1. Instructions for Use 2
2. Practice Questions with Answers & Rationales 2
BIO 181 · Arizona State University Page 1
, ASU BIO 181 EXAM 2 (MODULES 7-12) PRACTICE GUIDE METABOLISM, IMMUNOLOGY & GENETICS
How to Use This Guide
Read each stem, choose your answer, then check the rationale below. The correct option is marked, and each wrong option
is explained. This guide contains 76 questions covering the full scope of the ASU BIO 181 Exam 2 (modules 7-12).
Category: ASU BIO 181 — Exam 2 (modules 7-12)
1 Which enzyme unwraps the double helix?
A Helicase
B Primase
C DNA Polymerase III
D Ligase
Why A is correct: Helicase unwinds the double helix by breaking hydrogen bonds between base pairs during DNA
replication.
B — Primase synthesizes RNA primers.
C — DNA Polymerase III synthesizes new DNA.
D — Ligase joins Okazaki fragments.
2 Which enzyme is used first to permit DNA polymerase III to begin replicating the 3' strand?
A Primase
B Helicase
C Ligase
D Topoisomerase
Why A is correct: Primase synthesizes an RNA primer, which is required for DNA Polymerase III to begin replication.
B — Helicase unwinds DNA but does not synthesize primers.
C — Ligase joins fragments after replication.
D — Topoisomerase relieves supercoiling.
