PCB 3023 Cell Bio Exam 2 | Questions and
Correct Answers | Already Graded A+ | Newly
Updated 2026-2027
1. What is the Central Dogma of molecular biology?
A) The process by which protein is transcribed into RNA, which is then translated
into DNA
B) The process by which DNA is transcribed into RNA, which is then translated into
protein
C) The process by which RNA is transcribed into DNA, which is then translated into
protein
D) The process by which DNA is directly translated into protein
Correct Answer: B) The process by which DNA is transcribed into RNA, which is
then translated into protein
Rationale: The Central Dogma describes the flow of genetic information: DNA →
RNA → Protein. DNA is transcribed into RNA, and RNA is translated into protein.
This is the fundamental principle of molecular biology.
2. What are the two main processes involved in gene expression?
A) Replication and Translation
B) Transcription and Replication
C) Transcription (from DNA to RNA) and Translation (from RNA to protein)
D) Translation and Protein Folding
Correct Answer: C) Transcription (from DNA to RNA) and Translation (from RNA to
protein)
Rationale: Gene expression involves two key steps: (1) Transcription—synthesis of
RNA from a DNA template, and (2) Translation—synthesis of protein from an RNA
template. These processes convert the genetic code into functional products.
,3. How does a cell regulate the amount of protein produced?
A) By degrading all mRNA immediately after synthesis
B) By varying the rates of transcription and translation for different genes
C) By keeping all genes constantly active
D) By synthesizing proteins only in the nucleus
Correct Answer: B) By varying the rates of transcription and translation for
different genes
Rationale: Cells control protein production by regulating the rates of transcription
(how much mRNA is made) and translation (how efficiently mRNA is translated).
Different genes can be turned on/off or up/down regulated in response to cellular
needs.
4. What is the role of RNA polymerase in transcription?
A) It translates RNA into protein
B) It transcribes DNA into RNA by adding ribonucleotides to the growing RNA
chain
C) It replicates DNA by adding deoxyribonucleotides
D) It splices introns out of pre-mRNA
Correct Answer: B) It transcribes DNA into RNA by adding ribonucleotides to the
growing RNA chain
Rationale: RNA polymerase is the enzyme responsible for transcription. It binds to
the DNA template, unwinds it, and adds complementary ribonucleotides to the
growing RNA chain, using the DNA strand as a guide.
5. What is the difference between the template strand and the non-template
strand of DNA?
A) The template strand is used for RNA synthesis, while the non-template strand
(coding strand) has the same sequence as the RNA product (except for T replaced
by U)
B) Both strands are used for RNA synthesis
C) The template strand is never used, and the non-template strand is used for RNA
synthesis
,D) The template strand has the same sequence as the RNA product, and the non-
template strand is used for RNA synthesis
Correct Answer: A) The template strand is used for RNA synthesis, while the non-
template strand (coding strand) has the same sequence as the RNA product
(except for T replaced by U)
Rationale: During transcription, the template strand is read by RNA polymerase to
synthesize RNA. The non-template strand (coding strand) has the same sequence
as the RNA transcript, with thymine (T) replaced by uracil (U) in RNA.
6. What are the key differences between RNA and DNA?
A) RNA is double-stranded, contains deoxyribose, and uses thymine
B) RNA is mostly single-stranded, contains ribose sugar, and uses uracil instead of
thymine
C) RNA is double-stranded, contains ribose, and uses uracil
D) RNA is mostly single-stranded, contains deoxyribose, and uses thymine
Correct Answer: B) RNA is mostly single-stranded, contains ribose sugar, and uses
uracil instead of thymine
Rationale: RNA differs from DNA in three key ways: (1) RNA is usually single-
stranded (DNA is double-stranded), (2) RNA contains the sugar ribose (DNA has
deoxyribose), and (3) RNA uses uracil (U) instead of thymine (T).
7. What is the significance of the promoter in transcription?
A) It signals the end of transcription
B) It is a specific DNA sequence that signals RNA polymerase where to start
transcription
C) It codes for the protein product
D) It splices introns out of the pre-mRNA
Correct Answer: B) It is a specific DNA sequence that signals RNA polymerase
where to start transcription
Rationale: The promoter is a DNA sequence upstream of a gene that serves as a
binding site for RNA polymerase and transcription factors. It signals where
transcription should begin and determines which strand is used as the template.
, 8. What is a terminator in the context of transcription?
A) A sequence in DNA that signals the start of transcription
B) A sequence in DNA that signals the end of transcription, causing RNA
polymerase to stop and release the RNA transcript
C) A sequence in RNA that signals translation to stop
D) A protein that terminates transcription
Correct Answer: B) A sequence in DNA that signals the end of transcription,
causing RNA polymerase to stop and release the RNA transcript
Rationale: The terminator is a DNA sequence that signals the end of transcription.
When RNA polymerase reaches it, the enzyme releases the newly synthesized
RNA transcript and dissociates from the DNA.
9. How do bacterial and eukaryotic transcription differ?
A) Bacterial RNA polymerase can initiate transcription on its own, while eukaryotic
RNA polymerase requires additional transcription factors
B) Eukaryotic RNA polymerase can initiate transcription on its own, while bacterial
RNA polymerase requires additional transcription factors
C) Both require transcription factors for initiation
D) Neither requires transcription factors for initiation
Correct Answer: A) Bacterial RNA polymerase can initiate transcription on its
own, while eukaryotic RNA polymerase requires additional transcription factors
Rationale: Bacterial RNA polymerase (with sigma factor) can bind directly to the
promoter and initiate transcription. Eukaryotic RNA polymerase requires a
complex set of general transcription factors to assemble at the promoter and
initiate transcription.
10. What is the TATA box?
A) A DNA sequence in the promoter region recognized by transcription factors,
crucial for initiating transcription in eukaryotes
B) An RNA sequence that codes for methionine
Correct Answers | Already Graded A+ | Newly
Updated 2026-2027
1. What is the Central Dogma of molecular biology?
A) The process by which protein is transcribed into RNA, which is then translated
into DNA
B) The process by which DNA is transcribed into RNA, which is then translated into
protein
C) The process by which RNA is transcribed into DNA, which is then translated into
protein
D) The process by which DNA is directly translated into protein
Correct Answer: B) The process by which DNA is transcribed into RNA, which is
then translated into protein
Rationale: The Central Dogma describes the flow of genetic information: DNA →
RNA → Protein. DNA is transcribed into RNA, and RNA is translated into protein.
This is the fundamental principle of molecular biology.
2. What are the two main processes involved in gene expression?
A) Replication and Translation
B) Transcription and Replication
C) Transcription (from DNA to RNA) and Translation (from RNA to protein)
D) Translation and Protein Folding
Correct Answer: C) Transcription (from DNA to RNA) and Translation (from RNA to
protein)
Rationale: Gene expression involves two key steps: (1) Transcription—synthesis of
RNA from a DNA template, and (2) Translation—synthesis of protein from an RNA
template. These processes convert the genetic code into functional products.
,3. How does a cell regulate the amount of protein produced?
A) By degrading all mRNA immediately after synthesis
B) By varying the rates of transcription and translation for different genes
C) By keeping all genes constantly active
D) By synthesizing proteins only in the nucleus
Correct Answer: B) By varying the rates of transcription and translation for
different genes
Rationale: Cells control protein production by regulating the rates of transcription
(how much mRNA is made) and translation (how efficiently mRNA is translated).
Different genes can be turned on/off or up/down regulated in response to cellular
needs.
4. What is the role of RNA polymerase in transcription?
A) It translates RNA into protein
B) It transcribes DNA into RNA by adding ribonucleotides to the growing RNA
chain
C) It replicates DNA by adding deoxyribonucleotides
D) It splices introns out of pre-mRNA
Correct Answer: B) It transcribes DNA into RNA by adding ribonucleotides to the
growing RNA chain
Rationale: RNA polymerase is the enzyme responsible for transcription. It binds to
the DNA template, unwinds it, and adds complementary ribonucleotides to the
growing RNA chain, using the DNA strand as a guide.
5. What is the difference between the template strand and the non-template
strand of DNA?
A) The template strand is used for RNA synthesis, while the non-template strand
(coding strand) has the same sequence as the RNA product (except for T replaced
by U)
B) Both strands are used for RNA synthesis
C) The template strand is never used, and the non-template strand is used for RNA
synthesis
,D) The template strand has the same sequence as the RNA product, and the non-
template strand is used for RNA synthesis
Correct Answer: A) The template strand is used for RNA synthesis, while the non-
template strand (coding strand) has the same sequence as the RNA product
(except for T replaced by U)
Rationale: During transcription, the template strand is read by RNA polymerase to
synthesize RNA. The non-template strand (coding strand) has the same sequence
as the RNA transcript, with thymine (T) replaced by uracil (U) in RNA.
6. What are the key differences between RNA and DNA?
A) RNA is double-stranded, contains deoxyribose, and uses thymine
B) RNA is mostly single-stranded, contains ribose sugar, and uses uracil instead of
thymine
C) RNA is double-stranded, contains ribose, and uses uracil
D) RNA is mostly single-stranded, contains deoxyribose, and uses thymine
Correct Answer: B) RNA is mostly single-stranded, contains ribose sugar, and uses
uracil instead of thymine
Rationale: RNA differs from DNA in three key ways: (1) RNA is usually single-
stranded (DNA is double-stranded), (2) RNA contains the sugar ribose (DNA has
deoxyribose), and (3) RNA uses uracil (U) instead of thymine (T).
7. What is the significance of the promoter in transcription?
A) It signals the end of transcription
B) It is a specific DNA sequence that signals RNA polymerase where to start
transcription
C) It codes for the protein product
D) It splices introns out of the pre-mRNA
Correct Answer: B) It is a specific DNA sequence that signals RNA polymerase
where to start transcription
Rationale: The promoter is a DNA sequence upstream of a gene that serves as a
binding site for RNA polymerase and transcription factors. It signals where
transcription should begin and determines which strand is used as the template.
, 8. What is a terminator in the context of transcription?
A) A sequence in DNA that signals the start of transcription
B) A sequence in DNA that signals the end of transcription, causing RNA
polymerase to stop and release the RNA transcript
C) A sequence in RNA that signals translation to stop
D) A protein that terminates transcription
Correct Answer: B) A sequence in DNA that signals the end of transcription,
causing RNA polymerase to stop and release the RNA transcript
Rationale: The terminator is a DNA sequence that signals the end of transcription.
When RNA polymerase reaches it, the enzyme releases the newly synthesized
RNA transcript and dissociates from the DNA.
9. How do bacterial and eukaryotic transcription differ?
A) Bacterial RNA polymerase can initiate transcription on its own, while eukaryotic
RNA polymerase requires additional transcription factors
B) Eukaryotic RNA polymerase can initiate transcription on its own, while bacterial
RNA polymerase requires additional transcription factors
C) Both require transcription factors for initiation
D) Neither requires transcription factors for initiation
Correct Answer: A) Bacterial RNA polymerase can initiate transcription on its
own, while eukaryotic RNA polymerase requires additional transcription factors
Rationale: Bacterial RNA polymerase (with sigma factor) can bind directly to the
promoter and initiate transcription. Eukaryotic RNA polymerase requires a
complex set of general transcription factors to assemble at the promoter and
initiate transcription.
10. What is the TATA box?
A) A DNA sequence in the promoter region recognized by transcription factors,
crucial for initiating transcription in eukaryotes
B) An RNA sequence that codes for methionine
