Advanced Molecular Biology Multiple Choice
Questions (MCQs) with Answers and
Explanations for Degree, Master's, and
Professional Examinations
1. A mutation in the TATA-binding protein prevents efficient recognition of promoter
sequences in a eukaryotic cell. Which process would be most directly impaired?
A. DNA replication
B. RNA processing
C. Translation initiation
D. Transcription initiation
Explanation: The TATA-binding protein is a component of transcription factor TFIID and is
essential for assembly of the transcription initiation complex on many eukaryotic promoters.
2. Which enzyme is primarily responsible for relieving supercoiling ahead of the replication
fork in prokaryotes?
A. DNA polymerase III
B. Primase
C. DNA ligase
D. DNA gyrase
Explanation: DNA gyrase, a type II topoisomerase, introduces negative supercoils and alleviates
torsional stress generated during DNA replication.
3. In eukaryotic cells, which RNA polymerase synthesizes messenger RNA?
A. RNA polymerase I
B. RNA polymerase II
C. RNA polymerase III
D. Reverse transcriptase
, Explanation: RNA polymerase II transcribes protein-coding genes and produces precursor
mRNA molecules.
4. A mutation abolishes the proofreading activity of DNA polymerase. Which consequence
is most likely?
A. Reduced transcription efficiency
B. Increased recombination frequency
C. Failure of chromosome segregation
D. Increased mutation rate
Explanation: Proofreading activity corrects misincorporated nucleotides during DNA synthesis;
loss of this activity increases replication errors.
5. Which feature distinguishes eukaryotic mRNA from prokaryotic mRNA?
A. Presence of codons
B. Use of ribosomes
C. Requirement for tRNA
D. 5′ methylguanosine cap
Explanation: Most eukaryotic mRNAs possess a 5′ cap that enhances stability and translation
efficiency.
6. Which mechanism contributes most directly to genetic diversity during meiosis?
A. DNA repair
B. Transcriptional activation
C. Translation initiation
D. Homologous recombination
Explanation: Crossing-over between homologous chromosomes creates new combinations of
alleles and increases genetic variation.
7. In the lac operon, lactose functions primarily by:
A. Activating RNA polymerase directly
Questions (MCQs) with Answers and
Explanations for Degree, Master's, and
Professional Examinations
1. A mutation in the TATA-binding protein prevents efficient recognition of promoter
sequences in a eukaryotic cell. Which process would be most directly impaired?
A. DNA replication
B. RNA processing
C. Translation initiation
D. Transcription initiation
Explanation: The TATA-binding protein is a component of transcription factor TFIID and is
essential for assembly of the transcription initiation complex on many eukaryotic promoters.
2. Which enzyme is primarily responsible for relieving supercoiling ahead of the replication
fork in prokaryotes?
A. DNA polymerase III
B. Primase
C. DNA ligase
D. DNA gyrase
Explanation: DNA gyrase, a type II topoisomerase, introduces negative supercoils and alleviates
torsional stress generated during DNA replication.
3. In eukaryotic cells, which RNA polymerase synthesizes messenger RNA?
A. RNA polymerase I
B. RNA polymerase II
C. RNA polymerase III
D. Reverse transcriptase
, Explanation: RNA polymerase II transcribes protein-coding genes and produces precursor
mRNA molecules.
4. A mutation abolishes the proofreading activity of DNA polymerase. Which consequence
is most likely?
A. Reduced transcription efficiency
B. Increased recombination frequency
C. Failure of chromosome segregation
D. Increased mutation rate
Explanation: Proofreading activity corrects misincorporated nucleotides during DNA synthesis;
loss of this activity increases replication errors.
5. Which feature distinguishes eukaryotic mRNA from prokaryotic mRNA?
A. Presence of codons
B. Use of ribosomes
C. Requirement for tRNA
D. 5′ methylguanosine cap
Explanation: Most eukaryotic mRNAs possess a 5′ cap that enhances stability and translation
efficiency.
6. Which mechanism contributes most directly to genetic diversity during meiosis?
A. DNA repair
B. Transcriptional activation
C. Translation initiation
D. Homologous recombination
Explanation: Crossing-over between homologous chromosomes creates new combinations of
alleles and increases genetic variation.
7. In the lac operon, lactose functions primarily by:
A. Activating RNA polymerase directly
