Bio 93: Midterm Review | Test Questions
and Answers| 2025/2026
What is the central dogma of molecular biology?
The central dogma describes the flow of genetic information from DNA to RNA to protein.
What is the primary role of RNA polymerase during transcription?
RNA polymerase synthesizes a complementary RNA strand from a DNA template.
What is the function of the promoter region in a gene?
The promoter is a DNA sequence where RNA polymerase binds to initiate transcription.
How does alternative splicing contribute to protein diversity?
Alternative splicing allows a single gene to produce multiple protein isoforms by including
or excluding different exons.
What is the role of the 5' cap and the poly-A tail in eukaryotic mRNA?
The 5' cap and poly-A tail protect mRNA from degradation and assist in translation initiation.
How do repressors regulate gene expression in prokaryotes?
Repressors bind to the operator region of an operon to prevent RNA polymerase from
transcribing the downstream genes.
1
,What is the difference between a codon and an anticodon?
A codon is a three-nucleotide sequence in mRNA that specifies an amino acid, while an
anticodon is a complementary three-nucleotide sequence on a tRNA molecule.
What is the purpose of tRNA during translation?
tRNA delivers specific amino acids to the ribosome based on the codon-anticodon pairing.
Why is the genetic code described as "degenerate"?
The genetic code is degenerate because multiple codons can code for the same amino acid.
What is a polysome, and what is its function?
A polysome is a group of ribosomes translating a single mRNA simultaneously, increasing
protein production efficiency.
How does the ribosome know where to start translation?
The ribosome recognizes the start codon (AUG) in the mRNA and initiates translation there.
What are the main steps of translation?
Translation consists of initiation, elongation, and termination.
What is the function of the Shine-Dalgarno sequence in prokaryotic translation?
2
, The Shine-Dalgarno sequence helps the ribosome bind to the mRNA upstream of the start
codon.
How is gene expression regulated at the transcriptional level in eukaryotes?
Gene expression is regulated by transcription factors, enhancers, silencers, and chromatin
modifications.
What is a point mutation, and how can it affect gene expression?
A point mutation is a single nucleotide change that can lead to a silent, missense, or nonsense
mutation, altering the resulting protein.
What role does the A site of the ribosome play during translation?
The A site holds the incoming tRNA with its amino acid during translation.
What is the role of elongation factors in translation?
Elongation factors assist in the accurate delivery of tRNA to the ribosome and facilitate
translocation of the ribosome along the mRNA.
How does a nonsense mutation affect translation?
A nonsense mutation introduces a premature stop codon, leading to a truncated and often
nonfunctional protein.
What is the role of aminoacyl-tRNA synthetase?
3
, Aminoacyl-tRNA synthetase attaches the correct amino acid to its corresponding tRNA
molecule.
What is the role of the TATA box in transcription?
The TATA box is a DNA sequence in the promoter region that helps position RNA
polymerase in eukaryotes.
How do ribosomes in eukaryotic cells differ from those in prokaryotic cells?
Eukaryotic ribosomes are larger (80S) than prokaryotic ribosomes (70S) and differ slightly in
structure.
What is the role of release factors during translation termination?
Release factors recognize stop codons and promote the release of the polypeptide from the
ribosome.
What are operons, and why are they important in prokaryotic gene regulation?
Operons are clusters of genes regulated together by a single promoter, allowing coordinated
gene expression.
How does methylation of DNA affect gene expression?
Methylation typically represses gene expression by preventing transcription factor binding.
What is the wobble hypothesis, and how does it relate to tRNA?
4
and Answers| 2025/2026
What is the central dogma of molecular biology?
The central dogma describes the flow of genetic information from DNA to RNA to protein.
What is the primary role of RNA polymerase during transcription?
RNA polymerase synthesizes a complementary RNA strand from a DNA template.
What is the function of the promoter region in a gene?
The promoter is a DNA sequence where RNA polymerase binds to initiate transcription.
How does alternative splicing contribute to protein diversity?
Alternative splicing allows a single gene to produce multiple protein isoforms by including
or excluding different exons.
What is the role of the 5' cap and the poly-A tail in eukaryotic mRNA?
The 5' cap and poly-A tail protect mRNA from degradation and assist in translation initiation.
How do repressors regulate gene expression in prokaryotes?
Repressors bind to the operator region of an operon to prevent RNA polymerase from
transcribing the downstream genes.
1
,What is the difference between a codon and an anticodon?
A codon is a three-nucleotide sequence in mRNA that specifies an amino acid, while an
anticodon is a complementary three-nucleotide sequence on a tRNA molecule.
What is the purpose of tRNA during translation?
tRNA delivers specific amino acids to the ribosome based on the codon-anticodon pairing.
Why is the genetic code described as "degenerate"?
The genetic code is degenerate because multiple codons can code for the same amino acid.
What is a polysome, and what is its function?
A polysome is a group of ribosomes translating a single mRNA simultaneously, increasing
protein production efficiency.
How does the ribosome know where to start translation?
The ribosome recognizes the start codon (AUG) in the mRNA and initiates translation there.
What are the main steps of translation?
Translation consists of initiation, elongation, and termination.
What is the function of the Shine-Dalgarno sequence in prokaryotic translation?
2
, The Shine-Dalgarno sequence helps the ribosome bind to the mRNA upstream of the start
codon.
How is gene expression regulated at the transcriptional level in eukaryotes?
Gene expression is regulated by transcription factors, enhancers, silencers, and chromatin
modifications.
What is a point mutation, and how can it affect gene expression?
A point mutation is a single nucleotide change that can lead to a silent, missense, or nonsense
mutation, altering the resulting protein.
What role does the A site of the ribosome play during translation?
The A site holds the incoming tRNA with its amino acid during translation.
What is the role of elongation factors in translation?
Elongation factors assist in the accurate delivery of tRNA to the ribosome and facilitate
translocation of the ribosome along the mRNA.
How does a nonsense mutation affect translation?
A nonsense mutation introduces a premature stop codon, leading to a truncated and often
nonfunctional protein.
What is the role of aminoacyl-tRNA synthetase?
3
, Aminoacyl-tRNA synthetase attaches the correct amino acid to its corresponding tRNA
molecule.
What is the role of the TATA box in transcription?
The TATA box is a DNA sequence in the promoter region that helps position RNA
polymerase in eukaryotes.
How do ribosomes in eukaryotic cells differ from those in prokaryotic cells?
Eukaryotic ribosomes are larger (80S) than prokaryotic ribosomes (70S) and differ slightly in
structure.
What is the role of release factors during translation termination?
Release factors recognize stop codons and promote the release of the polypeptide from the
ribosome.
What are operons, and why are they important in prokaryotic gene regulation?
Operons are clusters of genes regulated together by a single promoter, allowing coordinated
gene expression.
How does methylation of DNA affect gene expression?
Methylation typically represses gene expression by preventing transcription factor binding.
What is the wobble hypothesis, and how does it relate to tRNA?
4
