BIOL101 Essential Biology Module 4
Comprehensive Practice Test with
Rationales
100 Questions | Detailed Explanations for
Every Answer
SECTION A: DNA & RNA STRUCTURE (Questions 1–10)
Question 1
The backbone of a DNA strand is composed of alternating
__________ and __________.
A) sugars; phosphates
B) bases; sugars
,C) phosphates; bases
D) amino acids; sugars
Correct Answer: A) sugars; phosphates
Rationale: The DNA backbone consists of deoxyribose sugar
and phosphate groups linked by phosphodiester bonds. The
nitrogenous bases project inward and pair with complementary
bases on the opposite strand.
Question 2
Which of the following correctly lists the pyrimidines found in
DNA?
A) Adenine, Guanine
B) Cytosine, Thymine
C) Cytosine, Uracil
D) Adenine, Thymine
Correct Answer: B) Cytosine, Thymine
,Rationale: Pyrimidines have a single ring. In DNA, they are
cytosine (C) and thymine (T). In RNA, uracil (U) replaces
thymine.
Question 3
If a DNA strand has the sequence 5′-AATCGG-3′, what is the
sequence of its complementary strand (written 3′→5′)?
A) 3′-TTAGCC-5′
B) 5′-CCGATT-3′
C) 3′-CCGATT-5′
D) 5′-AATCGG-3′
Correct Answer: A) 3′-TTAGCC-5′
Rationale: A pairs with T, and G pairs with C. The
complementary strand runs antiparallel, so if the given strand is
5′ to 3′, the complement is written 3′ to 5′.
Question 4
, In RNA, the sugar is ribose; in DNA, the sugar is __________.
A) glucose
B) deoxyribose
C) fructose
D) maltose
Correct Answer: B) deoxyribose
Rationale: Deoxyribose lacks an oxygen atom at the 2′ carbon,
making DNA more chemically stable than RNA.
Question 5
True or False: Hydrogen bonds hold the two strands of DNA
together.
A) True
B) False
Correct Answer: A) True
Rationale: Weak hydrogen bonds between complementary
base pairs (A-T: 2 bonds; G-C: 3 bonds) hold the double helix
together while still allowing strands to separate for replication.
Comprehensive Practice Test with
Rationales
100 Questions | Detailed Explanations for
Every Answer
SECTION A: DNA & RNA STRUCTURE (Questions 1–10)
Question 1
The backbone of a DNA strand is composed of alternating
__________ and __________.
A) sugars; phosphates
B) bases; sugars
,C) phosphates; bases
D) amino acids; sugars
Correct Answer: A) sugars; phosphates
Rationale: The DNA backbone consists of deoxyribose sugar
and phosphate groups linked by phosphodiester bonds. The
nitrogenous bases project inward and pair with complementary
bases on the opposite strand.
Question 2
Which of the following correctly lists the pyrimidines found in
DNA?
A) Adenine, Guanine
B) Cytosine, Thymine
C) Cytosine, Uracil
D) Adenine, Thymine
Correct Answer: B) Cytosine, Thymine
,Rationale: Pyrimidines have a single ring. In DNA, they are
cytosine (C) and thymine (T). In RNA, uracil (U) replaces
thymine.
Question 3
If a DNA strand has the sequence 5′-AATCGG-3′, what is the
sequence of its complementary strand (written 3′→5′)?
A) 3′-TTAGCC-5′
B) 5′-CCGATT-3′
C) 3′-CCGATT-5′
D) 5′-AATCGG-3′
Correct Answer: A) 3′-TTAGCC-5′
Rationale: A pairs with T, and G pairs with C. The
complementary strand runs antiparallel, so if the given strand is
5′ to 3′, the complement is written 3′ to 5′.
Question 4
, In RNA, the sugar is ribose; in DNA, the sugar is __________.
A) glucose
B) deoxyribose
C) fructose
D) maltose
Correct Answer: B) deoxyribose
Rationale: Deoxyribose lacks an oxygen atom at the 2′ carbon,
making DNA more chemically stable than RNA.
Question 5
True or False: Hydrogen bonds hold the two strands of DNA
together.
A) True
B) False
Correct Answer: A) True
Rationale: Weak hydrogen bonds between complementary
base pairs (A-T: 2 bonds; G-C: 3 bonds) hold the double helix
together while still allowing strands to separate for replication.
