Page 1 of 73
MCB 250 — EXAM 1 QUESTIONS WITH VERIFIED
QUESTIONS DETAILED RATIONALES GRADED A+
MCB 250 — Exam 1: Questions
SECTION 1: THE UNIVERSALITY OF MOLECULAR BIOLOGY (Questions 1–25)
1. Carl Woese's universal tree of life is based on DNA sequence comparisons of the gene
encoding what molecule?
A) 16s/18s small ribosomal subunit
B) DNA polymerase
C) Cytochrome c
D) ATP synthase
Answer: A
Rationale: Woese showed relationships between all life forms using the DNA sequence
comparison of the gene encoding the 16s/18s small ribosomal subunit .
2. Which three domains of life did Woese identify?
A) Bacteria, Archaea, and Eucarya
B) Prokaryotes, Eukaryotes, and Viruses
C) Plants, Animals, and Fungi
D) Monera, Protista, and Animalia
Answer: A
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Rationale: Woese taught us there are three large domains: Bacteria, Archaea, and Eucarya.
Archaea is a branch between Bacteria and Eucarya, sharing characteristics of both .
3. What is the fundamental difference between Bacteria and Eucarya?
A) Bacteria have a nucleus; Eucarya do not
B) Bacteria have no nucleus; Eucarya have a membrane-bound nucleus
C) Bacteria are larger than Eucarya
D) Bacteria use RNA; Eucarya use DNA
Answer: B
Rationale: Bacteria lack a nucleus, so DNA is in direct contact with the cytoplasm, and
transcription and translation are simultaneous. Eucarya contain a membrane-bound nucleus .
4. In prokaryotes, transcription and translation are:
A) Separated in time and space
B) Simultaneous
C) Independent processes
D) Only performed during cell division
Answer: B
Rationale: In bacteria, transcription and translation take place simultaneously in the same
cellular compartment—the cytoplasm .
5. Which model organism is used as the primary bacterial model?
A) Drosophila melanogaster
B) Escherichia coli
C) Danio rerio
D) Saccharomyces cerevisiae
Answer: B
Rationale: E. coli is the only bacteria model organism listed. Zebrafish and Drosophila flies are
eucaryal models .
6. The central dogma of molecular biology, proposed by Crick, states:
A) Protein → RNA → DNA
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B) DNA → RNA → Protein
C) RNA → DNA → Protein
D) DNA → Protein → RNA
Answer: B
Rationale: The central dogma states DNA makes RNA, and RNA makes protein. Reverse
transcription (RNA → DNA) is an exception found in retroviruses like HIV .
7. Which statement about RNA is correct?
A) RNA can only function as a messenger
B) RNA can have enzymatic and regulatory functions
C) RNA is always translated into protein
D) RNA cannot act alone
Answer: B
Rationale: RNA can have enzymatic and regulatory functions and can act alone, meaning it does
not always have to be translated into protein .
8. Metabolism is best defined as:
A) The breakdown of food only
B) The sum total of all chemical reactions of the cell
C) The synthesis of proteins only
D) The movement of molecules across membranes
Answer: B
Rationale: Metabolism is the sum total of all the chemical reactions of the cell. It includes both
catabolism and anabolism .
9. Catabolism refers to:
A) Synthesis of cell components
B) Breakdown of food to make energy
C) Protein folding
D) DNA replication
Answer: B
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Rationale: Catabolism is the breakdown of food to make energy. Anabolism is the synthesis of
components so cells can grow and divide .
10. Anabolism refers to:
A) Breakdown of food
B) Synthesis of components so cells can grow and divide
C) Energy production only
D) Waste removal
Answer: B
Rationale: Anabolism is the synthesis of cell components so cells can grow and divide .
11. Which of the following is NOT a function of proteins?
A) Catalyzing chemical reactions
B) Cell movement
C) Storing genetic information
D) Structural support
Answer: C
Rationale: Proteins catalyze reactions, allow cells to move, regulate biochemical processes, and
function as structural components. DNA stores genetic information .
12. Mitochondria are believed to have evolved from:
A) A gram-negative bacterial endosymbiont
B) A gram-positive bacterial endosymbiont
C) A eukaryotic organelle
D) A viral particle
Answer: A
Rationale: Mitochondria evolved from a gram-negative bacterial endosymbiont. The size of a
gram-negative bacterium is about the same size as the mitochondria .
13. Which of the following statements about in vitro vs. in vivo is correct?
A) In vitro means studying cells in their natural environment
B) In vitro refers to taking cells apart to see what each part does
MCB 250 — EXAM 1 QUESTIONS WITH VERIFIED
QUESTIONS DETAILED RATIONALES GRADED A+
MCB 250 — Exam 1: Questions
SECTION 1: THE UNIVERSALITY OF MOLECULAR BIOLOGY (Questions 1–25)
1. Carl Woese's universal tree of life is based on DNA sequence comparisons of the gene
encoding what molecule?
A) 16s/18s small ribosomal subunit
B) DNA polymerase
C) Cytochrome c
D) ATP synthase
Answer: A
Rationale: Woese showed relationships between all life forms using the DNA sequence
comparison of the gene encoding the 16s/18s small ribosomal subunit .
2. Which three domains of life did Woese identify?
A) Bacteria, Archaea, and Eucarya
B) Prokaryotes, Eukaryotes, and Viruses
C) Plants, Animals, and Fungi
D) Monera, Protista, and Animalia
Answer: A
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Rationale: Woese taught us there are three large domains: Bacteria, Archaea, and Eucarya.
Archaea is a branch between Bacteria and Eucarya, sharing characteristics of both .
3. What is the fundamental difference between Bacteria and Eucarya?
A) Bacteria have a nucleus; Eucarya do not
B) Bacteria have no nucleus; Eucarya have a membrane-bound nucleus
C) Bacteria are larger than Eucarya
D) Bacteria use RNA; Eucarya use DNA
Answer: B
Rationale: Bacteria lack a nucleus, so DNA is in direct contact with the cytoplasm, and
transcription and translation are simultaneous. Eucarya contain a membrane-bound nucleus .
4. In prokaryotes, transcription and translation are:
A) Separated in time and space
B) Simultaneous
C) Independent processes
D) Only performed during cell division
Answer: B
Rationale: In bacteria, transcription and translation take place simultaneously in the same
cellular compartment—the cytoplasm .
5. Which model organism is used as the primary bacterial model?
A) Drosophila melanogaster
B) Escherichia coli
C) Danio rerio
D) Saccharomyces cerevisiae
Answer: B
Rationale: E. coli is the only bacteria model organism listed. Zebrafish and Drosophila flies are
eucaryal models .
6. The central dogma of molecular biology, proposed by Crick, states:
A) Protein → RNA → DNA
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B) DNA → RNA → Protein
C) RNA → DNA → Protein
D) DNA → Protein → RNA
Answer: B
Rationale: The central dogma states DNA makes RNA, and RNA makes protein. Reverse
transcription (RNA → DNA) is an exception found in retroviruses like HIV .
7. Which statement about RNA is correct?
A) RNA can only function as a messenger
B) RNA can have enzymatic and regulatory functions
C) RNA is always translated into protein
D) RNA cannot act alone
Answer: B
Rationale: RNA can have enzymatic and regulatory functions and can act alone, meaning it does
not always have to be translated into protein .
8. Metabolism is best defined as:
A) The breakdown of food only
B) The sum total of all chemical reactions of the cell
C) The synthesis of proteins only
D) The movement of molecules across membranes
Answer: B
Rationale: Metabolism is the sum total of all the chemical reactions of the cell. It includes both
catabolism and anabolism .
9. Catabolism refers to:
A) Synthesis of cell components
B) Breakdown of food to make energy
C) Protein folding
D) DNA replication
Answer: B
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Rationale: Catabolism is the breakdown of food to make energy. Anabolism is the synthesis of
components so cells can grow and divide .
10. Anabolism refers to:
A) Breakdown of food
B) Synthesis of components so cells can grow and divide
C) Energy production only
D) Waste removal
Answer: B
Rationale: Anabolism is the synthesis of cell components so cells can grow and divide .
11. Which of the following is NOT a function of proteins?
A) Catalyzing chemical reactions
B) Cell movement
C) Storing genetic information
D) Structural support
Answer: C
Rationale: Proteins catalyze reactions, allow cells to move, regulate biochemical processes, and
function as structural components. DNA stores genetic information .
12. Mitochondria are believed to have evolved from:
A) A gram-negative bacterial endosymbiont
B) A gram-positive bacterial endosymbiont
C) A eukaryotic organelle
D) A viral particle
Answer: A
Rationale: Mitochondria evolved from a gram-negative bacterial endosymbiont. The size of a
gram-negative bacterium is about the same size as the mitochondria .
13. Which of the following statements about in vitro vs. in vivo is correct?
A) In vitro means studying cells in their natural environment
B) In vitro refers to taking cells apart to see what each part does
