,BIOD 101 Module 4 | Practice Q&A | 2026/2027 | Biology | Portage
Learning | 100% PASS
1. Which of the following is NOT one of the nitrogenous bases found in DNA?
A) Adenine
B) Guanine
C) Uracil
D) Thymine
Correct Answer: Uracil
Rationale: Uracil is found in RNA, not DNA. The four nitrogenous bases in
DNA are adenine, guanine, cytosine, and thymine. Uracil replaces thymine in
RNA. This is a fundamental distinction between DNA and RNA.
2. Purines contain how many carbon-nitrogen rings?
A) One
B) Two
C) Three
D) Four
Correct Answer: Two
Rationale: Purines contain two carbon-nitrogen rings and four nitrogen
atoms. Pyrimidines contain one carbon-nitrogen ring and two nitrogen atoms.
Adenine and guanine are purines; thymine and cytosine are pyrimidines.
3. Which of the following are purines?
A) Thymine and cytosine
,B) Adenine and guanine
C) Adenine and thymine
D) Guanine and cytosine
Correct Answer: Adenine and guanine
Rationale: Purines are adenine and guanine, which contain two carbon-
nitrogen rings. Pyrimidines are thymine and cytosine, which contain one
carbon-nitrogen ring. This classification is essential for understanding DNA
structure.
4. Which of the following are pyrimidines?
A) Adenine and guanine
B) Thymine and cytosine
C) Adenine and thymine
D) Guanine and cytosine
Correct Answer: Thymine and cytosine
Rationale: Pyrimidines are thymine and cytosine, which contain one carbon-
nitrogen ring. Purines are adenine and guanine, which contain two carbon-
nitrogen rings. This distinction is fundamental to nucleotide chemistry.
5. A nitrogenous base plus a deoxyribose sugar is called a:
A) Nucleotide
B) Nucleoside
C) Nitrogenous base
D) Polynucleotide
, Correct Answer: Nucleoside
Rationale: A nucleoside consists of a nitrogenous base plus a sugar
(deoxyribose in DNA). A nucleotide is a nucleoside plus a phosphate group.
This terminology distinction is commonly tested.
6. A nitrogenous base plus a deoxyribose sugar plus a phosphate group is
called a:
A) Nucleoside
B) Nitrogenous base
C) Nucleotide
D) Polynucleotide
Correct Answer: Nucleotide
Rationale: A nucleotide consists of a nitrogenous base, a sugar (deoxyribose
in DNA), and a phosphate group. A nucleoside lacks the phosphate group.
Nucleotides are the building blocks of DNA and RNA.
7. Describe the structure and arrangement of DNA.
A) DNA is a single helix with parallel strands held together by covalent bonds
B) DNA is a double helix with antiparallel strands held together by hydrogen
bonds between complementary bases
C) DNA is a double helix with parallel strands held together by ionic bonds
D) DNA is a single helix with antiparallel strands held together by peptide
bonds
Learning | 100% PASS
1. Which of the following is NOT one of the nitrogenous bases found in DNA?
A) Adenine
B) Guanine
C) Uracil
D) Thymine
Correct Answer: Uracil
Rationale: Uracil is found in RNA, not DNA. The four nitrogenous bases in
DNA are adenine, guanine, cytosine, and thymine. Uracil replaces thymine in
RNA. This is a fundamental distinction between DNA and RNA.
2. Purines contain how many carbon-nitrogen rings?
A) One
B) Two
C) Three
D) Four
Correct Answer: Two
Rationale: Purines contain two carbon-nitrogen rings and four nitrogen
atoms. Pyrimidines contain one carbon-nitrogen ring and two nitrogen atoms.
Adenine and guanine are purines; thymine and cytosine are pyrimidines.
3. Which of the following are purines?
A) Thymine and cytosine
,B) Adenine and guanine
C) Adenine and thymine
D) Guanine and cytosine
Correct Answer: Adenine and guanine
Rationale: Purines are adenine and guanine, which contain two carbon-
nitrogen rings. Pyrimidines are thymine and cytosine, which contain one
carbon-nitrogen ring. This classification is essential for understanding DNA
structure.
4. Which of the following are pyrimidines?
A) Adenine and guanine
B) Thymine and cytosine
C) Adenine and thymine
D) Guanine and cytosine
Correct Answer: Thymine and cytosine
Rationale: Pyrimidines are thymine and cytosine, which contain one carbon-
nitrogen ring. Purines are adenine and guanine, which contain two carbon-
nitrogen rings. This distinction is fundamental to nucleotide chemistry.
5. A nitrogenous base plus a deoxyribose sugar is called a:
A) Nucleotide
B) Nucleoside
C) Nitrogenous base
D) Polynucleotide
, Correct Answer: Nucleoside
Rationale: A nucleoside consists of a nitrogenous base plus a sugar
(deoxyribose in DNA). A nucleotide is a nucleoside plus a phosphate group.
This terminology distinction is commonly tested.
6. A nitrogenous base plus a deoxyribose sugar plus a phosphate group is
called a:
A) Nucleoside
B) Nitrogenous base
C) Nucleotide
D) Polynucleotide
Correct Answer: Nucleotide
Rationale: A nucleotide consists of a nitrogenous base, a sugar (deoxyribose
in DNA), and a phosphate group. A nucleoside lacks the phosphate group.
Nucleotides are the building blocks of DNA and RNA.
7. Describe the structure and arrangement of DNA.
A) DNA is a single helix with parallel strands held together by covalent bonds
B) DNA is a double helix with antiparallel strands held together by hydrogen
bonds between complementary bases
C) DNA is a double helix with parallel strands held together by ionic bonds
D) DNA is a single helix with antiparallel strands held together by peptide
bonds
