BIOL180 Unit Test 5 – DNA, RNA,
and Protein Synthesis Questions And
Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
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1. Which molecule stores the long-term hereditary information in
most living organisms?
A. ATP
B. RNA
C. Protein
D. DNA
Answer: D. DNA
Rationale: DNA, or deoxyribonucleic acid, is the primary molecule
responsible for storing hereditary information in cells. Its nucleotide
sequence contains the instructions needed for cellular structure,
function, growth, and reproduction.
2. Which three components make up a DNA nucleotide?
A. A phosphate group, deoxyribose sugar, and nitrogenous base
B. A phosphate group, ribose sugar, and amino acid
C. A fatty acid, glycerol, and nitrogenous base
D. A phosphate group, glucose, and amino acid
Answer: A. A phosphate group, deoxyribose sugar, and nitrogenous
base
,Rationale: Each DNA nucleotide consists of a phosphate group, a five-
carbon sugar called deoxyribose, and one nitrogenous base. The four
DNA bases are adenine, thymine, cytosine, and guanine.
3. Which nitrogenous bases are classified as purines?
A. Cytosine and thymine
B. Adenine and guanine
C. Adenine and thymine
D. Cytosine and guanine
Answer: B. Adenine and guanine
Rationale: Purines have a two-ring structure. Adenine and guanine are
the two purines found in DNA. Cytosine and thymine are pyrimidines
and contain a single nitrogen-containing ring.
4. In DNA, adenine pairs with which base?
A. Guanine
B. Cytosine
C. Thymine
D. Uracil
Answer: C. Thymine
Rationale: In DNA, adenine forms hydrogen bonds with thymine. This
complementary base pairing is essential for accurate DNA replication
and preservation of genetic information.
5. Which interaction holds complementary DNA bases together
between the two strands?
A. Hydrogen bonds
B. Peptide bonds
,C. Ionic bonds
D. Phosphodiester bonds
Answer: A. Hydrogen bonds
Rationale: Hydrogen bonds connect complementary nitrogenous bases
across the two DNA strands. Adenine and thymine form two hydrogen
bonds, while cytosine and guanine form three.
6. What does it mean that the two DNA strands are antiparallel?
A. They contain identical sequences in the same direction.
B. They contain different sugars.
C. They run in opposite 5′-to-3′ directions.
D. They are held together by peptide bonds.
Answer: C. They run in opposite 5′-to-3′ directions.
Rationale: The two strands of DNA are antiparallel because one strand
runs from 5′ to 3′ while the complementary strand runs from 3′ to 5′.
This orientation is important during DNA replication and
transcription.
7. What type of bond connects nucleotides within a single DNA
strand?
A. Hydrogen bond
B. Phosphodiester bond
C. Peptide bond
D. Glycosidic bond
Answer: B. Phosphodiester bond
Rationale: Phosphodiester bonds form the sugar-phosphate backbone
of DNA. A phosphate group connects the 3′ carbon of one sugar to the
5′ carbon of the next sugar.
, 8. Which statement best describes the structure of DNA?
A. A single-stranded chain of amino acids
B. A triple helix of carbohydrates
C. A circular chain of proteins
D. A double helix composed of two complementary nucleotide
strands
Answer: D. A double helix composed of two complementary nucleotide
strands
Rationale: DNA normally exists as a double helix consisting of two
antiparallel strands. Complementary base pairing allows the strands to
interact while preserving the information contained in their nucleotide
sequences.
9. Which DNA base contains a six-membered ring fused to a five-
membered ring?
A. Guanine
B. Thymine
C. Cytosine
D. Uracil
Answer: A. Guanine
Rationale: Guanine is a purine, meaning it contains two fused
nitrogen-containing rings. Adenine is the other purine. Cytosine,
thymine, and uracil are pyrimidines.
10. Which sugar is present in DNA?
A. Ribose
B. Glucose
C. Deoxyribose
D. Fructose
and Protein Synthesis Questions And
Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
Download Pdf
1. Which molecule stores the long-term hereditary information in
most living organisms?
A. ATP
B. RNA
C. Protein
D. DNA
Answer: D. DNA
Rationale: DNA, or deoxyribonucleic acid, is the primary molecule
responsible for storing hereditary information in cells. Its nucleotide
sequence contains the instructions needed for cellular structure,
function, growth, and reproduction.
2. Which three components make up a DNA nucleotide?
A. A phosphate group, deoxyribose sugar, and nitrogenous base
B. A phosphate group, ribose sugar, and amino acid
C. A fatty acid, glycerol, and nitrogenous base
D. A phosphate group, glucose, and amino acid
Answer: A. A phosphate group, deoxyribose sugar, and nitrogenous
base
,Rationale: Each DNA nucleotide consists of a phosphate group, a five-
carbon sugar called deoxyribose, and one nitrogenous base. The four
DNA bases are adenine, thymine, cytosine, and guanine.
3. Which nitrogenous bases are classified as purines?
A. Cytosine and thymine
B. Adenine and guanine
C. Adenine and thymine
D. Cytosine and guanine
Answer: B. Adenine and guanine
Rationale: Purines have a two-ring structure. Adenine and guanine are
the two purines found in DNA. Cytosine and thymine are pyrimidines
and contain a single nitrogen-containing ring.
4. In DNA, adenine pairs with which base?
A. Guanine
B. Cytosine
C. Thymine
D. Uracil
Answer: C. Thymine
Rationale: In DNA, adenine forms hydrogen bonds with thymine. This
complementary base pairing is essential for accurate DNA replication
and preservation of genetic information.
5. Which interaction holds complementary DNA bases together
between the two strands?
A. Hydrogen bonds
B. Peptide bonds
,C. Ionic bonds
D. Phosphodiester bonds
Answer: A. Hydrogen bonds
Rationale: Hydrogen bonds connect complementary nitrogenous bases
across the two DNA strands. Adenine and thymine form two hydrogen
bonds, while cytosine and guanine form three.
6. What does it mean that the two DNA strands are antiparallel?
A. They contain identical sequences in the same direction.
B. They contain different sugars.
C. They run in opposite 5′-to-3′ directions.
D. They are held together by peptide bonds.
Answer: C. They run in opposite 5′-to-3′ directions.
Rationale: The two strands of DNA are antiparallel because one strand
runs from 5′ to 3′ while the complementary strand runs from 3′ to 5′.
This orientation is important during DNA replication and
transcription.
7. What type of bond connects nucleotides within a single DNA
strand?
A. Hydrogen bond
B. Phosphodiester bond
C. Peptide bond
D. Glycosidic bond
Answer: B. Phosphodiester bond
Rationale: Phosphodiester bonds form the sugar-phosphate backbone
of DNA. A phosphate group connects the 3′ carbon of one sugar to the
5′ carbon of the next sugar.
, 8. Which statement best describes the structure of DNA?
A. A single-stranded chain of amino acids
B. A triple helix of carbohydrates
C. A circular chain of proteins
D. A double helix composed of two complementary nucleotide
strands
Answer: D. A double helix composed of two complementary nucleotide
strands
Rationale: DNA normally exists as a double helix consisting of two
antiparallel strands. Complementary base pairing allows the strands to
interact while preserving the information contained in their nucleotide
sequences.
9. Which DNA base contains a six-membered ring fused to a five-
membered ring?
A. Guanine
B. Thymine
C. Cytosine
D. Uracil
Answer: A. Guanine
Rationale: Guanine is a purine, meaning it contains two fused
nitrogen-containing rings. Adenine is the other purine. Cytosine,
thymine, and uracil are pyrimidines.
10. Which sugar is present in DNA?
A. Ribose
B. Glucose
C. Deoxyribose
D. Fructose
