BIOL101 Module 4 Test Bank
Essential Biology I w/Lab | 100
Comprehensive Exam Questions with
Verified Answers
SECTION 1: DNA & RNA STRUCTURE (Questions 1–15)
Question 1
Compare and contrast purines and pyrimidines. Provide
examples of each.
Verified Answer: Purines contain 2 carbon-nitrogen rings and
4 nitrogen atoms. Pyrimidines contain 1 carbon-nitrogen ring
and 2 nitrogen atoms. Purines include adenine and guanine.
Pyrimidines include thymine, cytosine, and uracil.
,Rationale: This structural difference is fundamental to
understanding DNA base pairing. Purines (double-ring
structures) always pair with pyrimidines (single-ring structures)
to maintain the uniform width of the DNA double helix.
Question 2
A nitrogenous base plus a deoxyribose is called a ________, and a
base plus deoxyribose plus a phosphate group is called a
________.
A) Nucleotide; Nucleoside
B) Nucleoside; Nucleotide
C) Chromatin; Chromosome
D) Codon; Anticodon
Correct Answer: B) Nucleoside; Nucleotide
Rationale: A nucleoside consists of a nitrogenous base
attached to a sugar (deoxyribose or ribose) but lacks a
phosphate group. When a phosphate group is added, it
becomes a nucleotide.
,Question 3
Which of the following nitrogenous bases are classified as
purines?
A) Cytosine and Thymine
B) Adenine and Guanine
C) Uracil and Cytosine
D) Thymine and Uracil
Correct Answer: B) Adenine and Guanine
Rationale: Purines have a double-ring structure. Adenine (A)
and Guanine (G) are the two purines found in nucleic acids.
Pyrimidines (C, T, U) have a single-ring structure.
Question 4
Which nitrogenous bases are classified as pyrimidines?
A) Adenine and Guanine
B) Cytosine, Thymine, and Uracil
, C) Adenine and Thymine
D) Guanine and Cytosine
Correct Answer: B) Cytosine, Thymine, and Uracil
Rationale: Pyrimidines have a single-ring structure. In DNA, the
pyrimidines are cytosine and thymine; in RNA, uracil replaces
thymine.
Question 5
In DNA, adenine always pairs with:
A) Guanine
B) Cytosine
C) Thymine
D) Uracil
Correct Answer: C) Thymine
Rationale: Complementary base pairing in DNA follows
Chargaff's rules: A pairs with T (two hydrogen bonds) and G
pairs with C (three hydrogen bonds). This specific pairing is
essential for accurate DNA replication.
Essential Biology I w/Lab | 100
Comprehensive Exam Questions with
Verified Answers
SECTION 1: DNA & RNA STRUCTURE (Questions 1–15)
Question 1
Compare and contrast purines and pyrimidines. Provide
examples of each.
Verified Answer: Purines contain 2 carbon-nitrogen rings and
4 nitrogen atoms. Pyrimidines contain 1 carbon-nitrogen ring
and 2 nitrogen atoms. Purines include adenine and guanine.
Pyrimidines include thymine, cytosine, and uracil.
,Rationale: This structural difference is fundamental to
understanding DNA base pairing. Purines (double-ring
structures) always pair with pyrimidines (single-ring structures)
to maintain the uniform width of the DNA double helix.
Question 2
A nitrogenous base plus a deoxyribose is called a ________, and a
base plus deoxyribose plus a phosphate group is called a
________.
A) Nucleotide; Nucleoside
B) Nucleoside; Nucleotide
C) Chromatin; Chromosome
D) Codon; Anticodon
Correct Answer: B) Nucleoside; Nucleotide
Rationale: A nucleoside consists of a nitrogenous base
attached to a sugar (deoxyribose or ribose) but lacks a
phosphate group. When a phosphate group is added, it
becomes a nucleotide.
,Question 3
Which of the following nitrogenous bases are classified as
purines?
A) Cytosine and Thymine
B) Adenine and Guanine
C) Uracil and Cytosine
D) Thymine and Uracil
Correct Answer: B) Adenine and Guanine
Rationale: Purines have a double-ring structure. Adenine (A)
and Guanine (G) are the two purines found in nucleic acids.
Pyrimidines (C, T, U) have a single-ring structure.
Question 4
Which nitrogenous bases are classified as pyrimidines?
A) Adenine and Guanine
B) Cytosine, Thymine, and Uracil
, C) Adenine and Thymine
D) Guanine and Cytosine
Correct Answer: B) Cytosine, Thymine, and Uracil
Rationale: Pyrimidines have a single-ring structure. In DNA, the
pyrimidines are cytosine and thymine; in RNA, uracil replaces
thymine.
Question 5
In DNA, adenine always pairs with:
A) Guanine
B) Cytosine
C) Thymine
D) Uracil
Correct Answer: C) Thymine
Rationale: Complementary base pairing in DNA follows
Chargaff's rules: A pairs with T (two hydrogen bonds) and G
pairs with C (three hydrogen bonds). This specific pairing is
essential for accurate DNA replication.
