Final Exam: BIOD 102/ BIOD102
(Latest 2025/ 2026 Update)
Essential Biology II W/Lab |
Questions & Answers| Grade A|
100% Correct (Verified
Solutions)- Portage Learning
1. Which feature of DNA allows each strand to serve as a template during
replication?
A. Its antiparallel, complementary base pairing
B. Its ability to form proteins
C. Its presence in ribosomes
D. Its single-stranded structure
Answer: A
Explanation: Complementary base pairing lets each parental strand
specify the sequence of a new strand.
2. Which enzyme unwinds the DNA double helix at a replication fork?
A. DNA ligase
B. Helicase
C. Primase
D. Telomerase
Answer: B
Explanation: Helicase separates the two DNA strands.
3. What is the primary role of DNA polymerase during replication?
A. Removing introns
B. Adding nucleotides to a growing DNA strand
C. Unwinding DNA
D. Joining chromosomes
BIOD 102 — Original Practice Edition Page 1
, Answer: B
Explanation: DNA polymerase synthesizes DNA by adding nucleotides to
the 3′ end.
4. Why is the lagging strand synthesized discontinuously?
A. DNA polymerase can synthesize only 5′→3′
B. The lagging strand contains RNA
C. Helicase works only on one strand
D. Ligase blocks continuous synthesis
Answer: A
Explanation: Because synthesis is 5′→3′ while the template strands are
antiparallel, the lagging strand is made in fragments.
5. Short DNA segments synthesized on the lagging strand are called what?
A. Introns
B. Codons
C. Okazaki fragments
D. Telomeres
Answer: C
Explanation: Okazaki fragments are later joined to form a continuous
strand.
6. Which enzyme joins adjacent DNA fragments by sealing the sugar-
phosphate backbone?
A. Ligase
B. Helicase
C. Primase
D. RNA polymerase
Answer: A
Explanation: DNA ligase forms phosphodiester bonds between DNA
fragments.
7. What is the function of primase?
A. Synthesizes a short RNA primer
B. Cuts out introns
C. Adds amino acids
D. Unwinds the entire chromosome
BIOD 102 — Original Practice Edition Page 2
, Answer: A
Explanation: Primase makes the RNA primer required for DNA
polymerase to begin synthesis.
8. A DNA molecule contains 30% adenine. Approximately what percentage
is cytosine?
A. 20%
B. 30%
C. 35%
D. 40%
Answer: A
Explanation: A=T, so T is 30%; the remaining 40% is G+C, making C 20%.
9. Which type of DNA repair corrects incorrectly paired bases that escape
proofreading?
A. Mismatch repair
B. TranscriptionC. Translation
D. RNA splicing
Answer: A
Explanation: Mismatch repair recognizes and replaces incorrectly paired
nucleotides after replication.
10. What is the main function of telomerase?
A. Extends chromosome ends
B. Removes RNA primers
C. Makes ribosomes
D. Cuts DNA at restriction sites
Answer: A
Explanation: Telomerase adds repetitive DNA to telomeres, helping
maintain chromosome ends.
11. Which nitrogenous bases are purines?
A. Cytosine and thymine
B. Adenine and guanine
C. Thymine and uracil
D. Cytosine and uracil
BIOD 102 — Original Practice Edition Page 3
, Answer: B
Explanation: Adenine and guanine are the two purines.
12. A mutation that changes one nucleotide but does not change the
encoded amino acid is calledwhat?
A. Nonsense
B. Missense
C. Silent
D. FrameshiftAnswer: C
Explanation: Because of genetic-code redundancy, some nucleotide
substitutions do not alter the amino acid.
13. What is the complementary DNA sequence to 5′-ATGC-3′?
A. 5′-TACG-3′
B. 3′-TACG-5′
C. 5′-UACG-3′
D. 3′-ATGC-5′
Answer: B
Explanation: The complementary strand is antiparallel: 3′-TACG-5′.
14. Which DNA damage can result from ultraviolet radiation?
A. Thymine dimers
B. Extra ribosomes
C. RNA primers
D. Amino-acid substitutions
Answer: A
Explanation: UV light can cause covalent bonds between adjacent
thymine bases.
15. What is semiconservative replication?
A. Each daughter DNA has one old and one new strand
B. Both daughter molecules contain only old DNA
C. Both strands are entirely new
D. Only RNA is copiedAnswer: A
Explanation: Each daughter DNA molecule retains one parental strand
and contains one newly synthesized strand.
16. What does proofreading by DNA polymerase primarily improve?
BIOD 102 — Original Practice Edition Page 4
(Latest 2025/ 2026 Update)
Essential Biology II W/Lab |
Questions & Answers| Grade A|
100% Correct (Verified
Solutions)- Portage Learning
1. Which feature of DNA allows each strand to serve as a template during
replication?
A. Its antiparallel, complementary base pairing
B. Its ability to form proteins
C. Its presence in ribosomes
D. Its single-stranded structure
Answer: A
Explanation: Complementary base pairing lets each parental strand
specify the sequence of a new strand.
2. Which enzyme unwinds the DNA double helix at a replication fork?
A. DNA ligase
B. Helicase
C. Primase
D. Telomerase
Answer: B
Explanation: Helicase separates the two DNA strands.
3. What is the primary role of DNA polymerase during replication?
A. Removing introns
B. Adding nucleotides to a growing DNA strand
C. Unwinding DNA
D. Joining chromosomes
BIOD 102 — Original Practice Edition Page 1
, Answer: B
Explanation: DNA polymerase synthesizes DNA by adding nucleotides to
the 3′ end.
4. Why is the lagging strand synthesized discontinuously?
A. DNA polymerase can synthesize only 5′→3′
B. The lagging strand contains RNA
C. Helicase works only on one strand
D. Ligase blocks continuous synthesis
Answer: A
Explanation: Because synthesis is 5′→3′ while the template strands are
antiparallel, the lagging strand is made in fragments.
5. Short DNA segments synthesized on the lagging strand are called what?
A. Introns
B. Codons
C. Okazaki fragments
D. Telomeres
Answer: C
Explanation: Okazaki fragments are later joined to form a continuous
strand.
6. Which enzyme joins adjacent DNA fragments by sealing the sugar-
phosphate backbone?
A. Ligase
B. Helicase
C. Primase
D. RNA polymerase
Answer: A
Explanation: DNA ligase forms phosphodiester bonds between DNA
fragments.
7. What is the function of primase?
A. Synthesizes a short RNA primer
B. Cuts out introns
C. Adds amino acids
D. Unwinds the entire chromosome
BIOD 102 — Original Practice Edition Page 2
, Answer: A
Explanation: Primase makes the RNA primer required for DNA
polymerase to begin synthesis.
8. A DNA molecule contains 30% adenine. Approximately what percentage
is cytosine?
A. 20%
B. 30%
C. 35%
D. 40%
Answer: A
Explanation: A=T, so T is 30%; the remaining 40% is G+C, making C 20%.
9. Which type of DNA repair corrects incorrectly paired bases that escape
proofreading?
A. Mismatch repair
B. TranscriptionC. Translation
D. RNA splicing
Answer: A
Explanation: Mismatch repair recognizes and replaces incorrectly paired
nucleotides after replication.
10. What is the main function of telomerase?
A. Extends chromosome ends
B. Removes RNA primers
C. Makes ribosomes
D. Cuts DNA at restriction sites
Answer: A
Explanation: Telomerase adds repetitive DNA to telomeres, helping
maintain chromosome ends.
11. Which nitrogenous bases are purines?
A. Cytosine and thymine
B. Adenine and guanine
C. Thymine and uracil
D. Cytosine and uracil
BIOD 102 — Original Practice Edition Page 3
, Answer: B
Explanation: Adenine and guanine are the two purines.
12. A mutation that changes one nucleotide but does not change the
encoded amino acid is calledwhat?
A. Nonsense
B. Missense
C. Silent
D. FrameshiftAnswer: C
Explanation: Because of genetic-code redundancy, some nucleotide
substitutions do not alter the amino acid.
13. What is the complementary DNA sequence to 5′-ATGC-3′?
A. 5′-TACG-3′
B. 3′-TACG-5′
C. 5′-UACG-3′
D. 3′-ATGC-5′
Answer: B
Explanation: The complementary strand is antiparallel: 3′-TACG-5′.
14. Which DNA damage can result from ultraviolet radiation?
A. Thymine dimers
B. Extra ribosomes
C. RNA primers
D. Amino-acid substitutions
Answer: A
Explanation: UV light can cause covalent bonds between adjacent
thymine bases.
15. What is semiconservative replication?
A. Each daughter DNA has one old and one new strand
B. Both daughter molecules contain only old DNA
C. Both strands are entirely new
D. Only RNA is copiedAnswer: A
Explanation: Each daughter DNA molecule retains one parental strand
and contains one newly synthesized strand.
16. What does proofreading by DNA polymerase primarily improve?
BIOD 102 — Original Practice Edition Page 4
