UCF BIOMEDICAL SCIENCES EXIT EXAM AND
STUDY GUIDE NEWEST 2026 TEST BANK| WITH
300 QUESTIONS
1. Which enzyme is responsible for synthesizing mRNA from a DNA template
during transcription?
a) DNA Polymerase III
b) Helicase
c) RNA Polymerase
d) Ligase
Answer: c
Rationale: RNA Polymerase catalyzes transcription by reading the DNA template
and assembling complementary RNA nucleotides. DNA Polymerase III is for DNA
replication, Helicase unwinds DNA, and Ligase joins Okazaki fragments.
2. A mutation occurs where an Adenine is replaced by a Guanine in the coding
strand of DNA. This is an example of a:
a) Frameshift mutation
b) Transition
c) Transversion
d) Silent mutation
Answer: b
Rationale: A transition is a purine-to-purine (A↔G) or pyrimidine-to-pyrimidine
(C↔T) substitution. A transversion is a purine-to-pyrimidine swap. Frameshifts
involve insertions/deletions.
3. During translation, the ribosome reads mRNA in codons. Which sequence acts
as the start codon in eukaryotes?
a) UAA
,b) UGA
c) AUG
d) TAG
Answer: c
Rationale: AUG codes for Methionine and serves as the universal start codon.
UAA and UGA are stop codons. TAG is a DNA stop codon (not mRNA).
4. The "wobble" hypothesis explains:
a) Why DNA is anti-parallel
b) Why the third base of a codon can pair loosely with the anticodon
c) How exons are spliced
d) How DNA polymerase proofreads
Answer: b
Rationale: Wobble allows a single tRNA anticodon to recognize more than one
codon due to flexible pairing at the 3rd nucleotide position, reducing the number
of tRNAs needed.
5. Which of the following is NOT a post-transcriptional modification in
eukaryotes?
a) 5' capping
b) Polyadenylation (3' poly-A tail)
c) Splicing of introns
d) Methylation of cytosines in DNA
Answer: d
Rationale: DNA methylation is an epigenetic modification, not a post-
transcriptional RNA modification. 5' capping, polyadenylation, and splicing occur
on pre-mRNA.
6. DNA Polymerase III synthesizes DNA in which direction?
a) 3' to 5'
,b) 5' to 3'
c) Both directions
d) Randomly
Answer: b
Rationale: All DNA polymerases synthesize new strands in the 5'→3' direction by
adding nucleotides to the 3'-OH group of the growing strand.
7. In the replication fork, the lagging strand is synthesized discontinuously as:
a) Leading strands
b) Okazaki fragments
c) Hairpin loops
d) Telomeres
Answer: b
Rationale: The lagging strand is synthesized away from the replication fork in
short Okazaki fragments, which are later joined by DNA ligase.
8. A patient has xeroderma pigmentosum, characterized by extreme sensitivity
to UV light. This disease is caused by a defect in:
a) Mismatch repair
b) Base excision repair
c) Nucleotide excision repair (NER)
d) Non-homologous end joining
Answer: c
Rationale: NER specifically removes bulky DNA lesions like thymine dimers caused
by UV radiation. Defects lead to XP.
9. Which enzyme is responsible for relieving supercoiling ahead of the
replication fork?
a) Helicase
b) Topoisomerase
, c) Primase
d) Telomerase
Answer: b
Rationale: Topoisomerase (e.g., gyrase in bacteria) cuts and rejoins DNA to relieve
torsional stress. Helicase unwinds; Primase synthesizes RNA primers; Telomerase
extends telomeres.
10. In most somatic cells, telomeres shorten with each division. Which enzyme
maintains them in germ cells and cancer cells?
a) DNA Polymerase
b) Telomerase
c) Ligase
d) RNase
Answer: b
Rationale: Telomerase adds repetitive sequences to chromosome ends using its
RNA template, counteracting the end-replication problem. It is active in stem cells,
germ cells, and most cancers.
11. The Lac Operon is induced by:
a) Glucose
b) Lactose (or allolactose)
c) Tryptophan
d) cAMP
Answer: b
Rationale: Allolactose, a metabolite of lactose, binds the Lac repressor,
inactivating it and allowing transcription. Glucose inhibits it via catabolite
repression.
12. DNA methylation typically leads to:
a) Increased transcription
STUDY GUIDE NEWEST 2026 TEST BANK| WITH
300 QUESTIONS
1. Which enzyme is responsible for synthesizing mRNA from a DNA template
during transcription?
a) DNA Polymerase III
b) Helicase
c) RNA Polymerase
d) Ligase
Answer: c
Rationale: RNA Polymerase catalyzes transcription by reading the DNA template
and assembling complementary RNA nucleotides. DNA Polymerase III is for DNA
replication, Helicase unwinds DNA, and Ligase joins Okazaki fragments.
2. A mutation occurs where an Adenine is replaced by a Guanine in the coding
strand of DNA. This is an example of a:
a) Frameshift mutation
b) Transition
c) Transversion
d) Silent mutation
Answer: b
Rationale: A transition is a purine-to-purine (A↔G) or pyrimidine-to-pyrimidine
(C↔T) substitution. A transversion is a purine-to-pyrimidine swap. Frameshifts
involve insertions/deletions.
3. During translation, the ribosome reads mRNA in codons. Which sequence acts
as the start codon in eukaryotes?
a) UAA
,b) UGA
c) AUG
d) TAG
Answer: c
Rationale: AUG codes for Methionine and serves as the universal start codon.
UAA and UGA are stop codons. TAG is a DNA stop codon (not mRNA).
4. The "wobble" hypothesis explains:
a) Why DNA is anti-parallel
b) Why the third base of a codon can pair loosely with the anticodon
c) How exons are spliced
d) How DNA polymerase proofreads
Answer: b
Rationale: Wobble allows a single tRNA anticodon to recognize more than one
codon due to flexible pairing at the 3rd nucleotide position, reducing the number
of tRNAs needed.
5. Which of the following is NOT a post-transcriptional modification in
eukaryotes?
a) 5' capping
b) Polyadenylation (3' poly-A tail)
c) Splicing of introns
d) Methylation of cytosines in DNA
Answer: d
Rationale: DNA methylation is an epigenetic modification, not a post-
transcriptional RNA modification. 5' capping, polyadenylation, and splicing occur
on pre-mRNA.
6. DNA Polymerase III synthesizes DNA in which direction?
a) 3' to 5'
,b) 5' to 3'
c) Both directions
d) Randomly
Answer: b
Rationale: All DNA polymerases synthesize new strands in the 5'→3' direction by
adding nucleotides to the 3'-OH group of the growing strand.
7. In the replication fork, the lagging strand is synthesized discontinuously as:
a) Leading strands
b) Okazaki fragments
c) Hairpin loops
d) Telomeres
Answer: b
Rationale: The lagging strand is synthesized away from the replication fork in
short Okazaki fragments, which are later joined by DNA ligase.
8. A patient has xeroderma pigmentosum, characterized by extreme sensitivity
to UV light. This disease is caused by a defect in:
a) Mismatch repair
b) Base excision repair
c) Nucleotide excision repair (NER)
d) Non-homologous end joining
Answer: c
Rationale: NER specifically removes bulky DNA lesions like thymine dimers caused
by UV radiation. Defects lead to XP.
9. Which enzyme is responsible for relieving supercoiling ahead of the
replication fork?
a) Helicase
b) Topoisomerase
, c) Primase
d) Telomerase
Answer: b
Rationale: Topoisomerase (e.g., gyrase in bacteria) cuts and rejoins DNA to relieve
torsional stress. Helicase unwinds; Primase synthesizes RNA primers; Telomerase
extends telomeres.
10. In most somatic cells, telomeres shorten with each division. Which enzyme
maintains them in germ cells and cancer cells?
a) DNA Polymerase
b) Telomerase
c) Ligase
d) RNase
Answer: b
Rationale: Telomerase adds repetitive sequences to chromosome ends using its
RNA template, counteracting the end-replication problem. It is active in stem cells,
germ cells, and most cancers.
11. The Lac Operon is induced by:
a) Glucose
b) Lactose (or allolactose)
c) Tryptophan
d) cAMP
Answer: b
Rationale: Allolactose, a metabolite of lactose, binds the Lac repressor,
inactivating it and allowing transcription. Glucose inhibits it via catabolite
repression.
12. DNA methylation typically leads to:
a) Increased transcription
