WGU C785 Biochemistry Exam 2 Practice 90 Questions | Accurate &
Verified Answers to Pass Actual Exam
1. What constitutes the backbone of a DNA double helix?
A. Nitrogenous bases and hydrogen bonds
B. Amino acids and peptide bonds
C. Deoxyribose sugars and phosphate groups
D. Ribose sugars and hydroxyl groups
Answer: C
Explanation: The sugar-phosphate backbone consists of alternating deoxyribose sugar and
phosphate groups linked by phosphodiester bonds.
2. Which enzyme is responsible for unwinding the DNA double helix during
replication?
A. DNA Polymerase
B. DNA Ligase
C. Primase
D. Helicase
Answer: D
,Explanation: Helicase breaks the hydrogen bonds between nitrogenous bases to separate
the DNA strands.
3. In which direction is a new DNA strand synthesized?
A. 3’ to 5’
B. N-terminus to C-terminus
C. 5’ to 3’
D. Randomly depending on the strand
Answer: C
Explanation: DNA Polymerase can only add nucleotides to the 3’ hydroxyl end of a
growing strand, meaning synthesis occurs 5’ to 3’.
4. What is the primary difference between DNA and RNA sugars?
A. RNA contains glucose while DNA contains ribose
B. There is no difference in the sugars used
C. RNA contains deoxyribose, which has an extra oxygen atom
D. DNA contains deoxyribose, which lacks an oxygen atom at the 2’ carbon
Answer: D
Explanation: Deoxyribose (DNA) lacks the hydroxyl (-OH) group at the 2’ carbon position
that is present in ribose (RNA).
,5. Which nitrogenous base is found in RNA but not in DNA?
A. Uracil
B. Adenine
C. Thymine
D. Guanine
Answer: A
Explanation: Uracil replaces thymine in RNA and pairs with adenine.
6. What are the short segments of DNA synthesized on the lagging strand
called?
A. Introns
B. Exons
C. Promoters
D. Okazaki fragments
Answer: D
Explanation: Because synthesis must occur 5’ to 3’, the lagging strand is made in short,
discontinuous pieces called Okazaki fragments.
7. Which enzyme joins Okazaki fragments together?
A. Helicase
B. RNA Polymerase
, C. Topoisomerase
D. DNA Ligase
Answer: D
Explanation: DNA ligase catalyzes the formation of the phosphodiester bond that seals the
gaps between DNA fragments.
8. What is the function of a promoter in transcription?
A. To signal the end of translation
B. To code for the poly-A tail
C. To provide a binding site for RNA polymerase to start transcription
D. To remove introns from the pre-mRNA
Answer: C
Explanation: A promoter is a specific DNA sequence where RNA polymerase binds to
initiate the transcription of a gene.
9. Which process involves removing non-coding regions from pre-mRNA?
A. Splicing
B. Capping
C. Translation
D. Polyadenylation
Answer: A
Verified Answers to Pass Actual Exam
1. What constitutes the backbone of a DNA double helix?
A. Nitrogenous bases and hydrogen bonds
B. Amino acids and peptide bonds
C. Deoxyribose sugars and phosphate groups
D. Ribose sugars and hydroxyl groups
Answer: C
Explanation: The sugar-phosphate backbone consists of alternating deoxyribose sugar and
phosphate groups linked by phosphodiester bonds.
2. Which enzyme is responsible for unwinding the DNA double helix during
replication?
A. DNA Polymerase
B. DNA Ligase
C. Primase
D. Helicase
Answer: D
,Explanation: Helicase breaks the hydrogen bonds between nitrogenous bases to separate
the DNA strands.
3. In which direction is a new DNA strand synthesized?
A. 3’ to 5’
B. N-terminus to C-terminus
C. 5’ to 3’
D. Randomly depending on the strand
Answer: C
Explanation: DNA Polymerase can only add nucleotides to the 3’ hydroxyl end of a
growing strand, meaning synthesis occurs 5’ to 3’.
4. What is the primary difference between DNA and RNA sugars?
A. RNA contains glucose while DNA contains ribose
B. There is no difference in the sugars used
C. RNA contains deoxyribose, which has an extra oxygen atom
D. DNA contains deoxyribose, which lacks an oxygen atom at the 2’ carbon
Answer: D
Explanation: Deoxyribose (DNA) lacks the hydroxyl (-OH) group at the 2’ carbon position
that is present in ribose (RNA).
,5. Which nitrogenous base is found in RNA but not in DNA?
A. Uracil
B. Adenine
C. Thymine
D. Guanine
Answer: A
Explanation: Uracil replaces thymine in RNA and pairs with adenine.
6. What are the short segments of DNA synthesized on the lagging strand
called?
A. Introns
B. Exons
C. Promoters
D. Okazaki fragments
Answer: D
Explanation: Because synthesis must occur 5’ to 3’, the lagging strand is made in short,
discontinuous pieces called Okazaki fragments.
7. Which enzyme joins Okazaki fragments together?
A. Helicase
B. RNA Polymerase
, C. Topoisomerase
D. DNA Ligase
Answer: D
Explanation: DNA ligase catalyzes the formation of the phosphodiester bond that seals the
gaps between DNA fragments.
8. What is the function of a promoter in transcription?
A. To signal the end of translation
B. To code for the poly-A tail
C. To provide a binding site for RNA polymerase to start transcription
D. To remove introns from the pre-mRNA
Answer: C
Explanation: A promoter is a specific DNA sequence where RNA polymerase binds to
initiate the transcription of a gene.
9. Which process involves removing non-coding regions from pre-mRNA?
A. Splicing
B. Capping
C. Translation
D. Polyadenylation
Answer: A
