ESTUDYR
BIO-205 MICROBIOLOGY MIDTERM MULTICHOICE ANSWERED
EXAM QUESTIONS WITH DETAILED RATIONALES
1. Why are fungi important in ecological and human systems?
A. They only cause disease in plants
B. They only help plants grow
C. They only spoil food
D. They help plants grow, cause plant diseases, make foods/beverages, and spoil food
✅Answer: D
Rationale: Fungi have diverse roles—symbiotic (mycorrhizae), pathogenic, industrial
(fermentation), and decompositional (food spoilage).
2. All fungi have which substance in their cell walls?
A. Cellulose
B. Peptidoglycan
C. Chitin
D. Lipopolysaccharide
✅Answer: C
Rationale: Chitin is the defining component of fungal cell walls and differentiates fungi from
plants and bacteria.
3. Transfer of bacterial DNA by bacteriophages is known as:
A. Transformation
B. Transduction
C. Conjugation
D. Transposition
✅Answer: B
Rationale: Transduction involves viruses acting as carriers of bacterial genes.
4. The source of variation among previously identical microorganisms is:
,ESTUDYR
A. Transduction
B. Recombination
C. Mutation
D. Transformation
✅Answer: C
Rationale: Random mutations produce genetic diversity in populations.
5. Intercalating agents typically cause:
A. Point mutations
B. Nonsense mutations
C. Frameshift mutations
D. Silent mutations
✅Answer: C
Rationale: They insert between DNA bases, disrupting reading frames during replication.
6. Which gene transfer method requires direct cell-to-cell contact?
A. Transformation
B. Transduction
C. Conjugation
D. Transposition
✅Answer: C
Rationale: Conjugation uses a pilus to transfer DNA between cells.
7. Mobile segments of DNA that move within the genome are called:
A. Plasmids
B. Transposons
C. Cosmid
D. Operons
✅Answer: B
Rationale: Transposons “jump” to new locations and may disrupt genes.
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8. Which method is commonly used to identify auxotrophic mutants?
A. Plaque assays
B. Replica plating
C. ELISA
D. Gram staining
✅Answer: B
Rationale: Replica plating detects cells that cannot grow on minimal media.
9. Thymine dimers formed by UV radiation are repaired by:
A. Conjugation
B. Photoreactivation and excision repair
C. Translation
D. Replication fork repair
✅Answer: B
Rationale: Photolyase breaks dimers; excision repair removes damaged bases.
10. UV irradiation of cells primarily causes:
A. Double-strand breaks
B. Frameshift mutations
C. Thymine dimers
D. Gene amplification
✅Answer: C
Rationale: UV light cross-links adjacent thymine bases, distorting DNA.
11. Fungi lacking observed sexual reproduction belong to which group?
A. Basidiomycetes
B. Deuteromycetes
C. Ascomycetes
D. Zygomycetes
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✅Answer: B
Rationale: Deuteromycetes = “imperfect fungi” because sexual forms are unknown.
12. A mass of fungal hyphae is called:
A. Thallus
B. Sporangium
C. Mycelium
D. Septum
✅Answer: C
Rationale: Hyphae collectively form a mycelium — the body of a fungus.
13. Which methods help identify and classify bacteria?
A. Only biochemical tests
B. Only nucleic acid tests
C. Microscopy, culture traits, biochemical tests, and nucleic acid analysis
D. Only Gram stain
✅Answer: C
Rationale: Modern taxonomy combines phenotypic and genotypic methods.
14. Lichens consist of:
A. Virus and fungus
B. Bacterium and fungus
C. Alga and fungus
D. Moss and fungus
✅Answer: C
Rationale: A fungal partner + a photosynthetic alga or cyanobacterium.
15. The terms yeast, mold, and mushroom refer to fungal:
BIO-205 MICROBIOLOGY MIDTERM MULTICHOICE ANSWERED
EXAM QUESTIONS WITH DETAILED RATIONALES
1. Why are fungi important in ecological and human systems?
A. They only cause disease in plants
B. They only help plants grow
C. They only spoil food
D. They help plants grow, cause plant diseases, make foods/beverages, and spoil food
✅Answer: D
Rationale: Fungi have diverse roles—symbiotic (mycorrhizae), pathogenic, industrial
(fermentation), and decompositional (food spoilage).
2. All fungi have which substance in their cell walls?
A. Cellulose
B. Peptidoglycan
C. Chitin
D. Lipopolysaccharide
✅Answer: C
Rationale: Chitin is the defining component of fungal cell walls and differentiates fungi from
plants and bacteria.
3. Transfer of bacterial DNA by bacteriophages is known as:
A. Transformation
B. Transduction
C. Conjugation
D. Transposition
✅Answer: B
Rationale: Transduction involves viruses acting as carriers of bacterial genes.
4. The source of variation among previously identical microorganisms is:
,ESTUDYR
A. Transduction
B. Recombination
C. Mutation
D. Transformation
✅Answer: C
Rationale: Random mutations produce genetic diversity in populations.
5. Intercalating agents typically cause:
A. Point mutations
B. Nonsense mutations
C. Frameshift mutations
D. Silent mutations
✅Answer: C
Rationale: They insert between DNA bases, disrupting reading frames during replication.
6. Which gene transfer method requires direct cell-to-cell contact?
A. Transformation
B. Transduction
C. Conjugation
D. Transposition
✅Answer: C
Rationale: Conjugation uses a pilus to transfer DNA between cells.
7. Mobile segments of DNA that move within the genome are called:
A. Plasmids
B. Transposons
C. Cosmid
D. Operons
✅Answer: B
Rationale: Transposons “jump” to new locations and may disrupt genes.
,ESTUDYR
8. Which method is commonly used to identify auxotrophic mutants?
A. Plaque assays
B. Replica plating
C. ELISA
D. Gram staining
✅Answer: B
Rationale: Replica plating detects cells that cannot grow on minimal media.
9. Thymine dimers formed by UV radiation are repaired by:
A. Conjugation
B. Photoreactivation and excision repair
C. Translation
D. Replication fork repair
✅Answer: B
Rationale: Photolyase breaks dimers; excision repair removes damaged bases.
10. UV irradiation of cells primarily causes:
A. Double-strand breaks
B. Frameshift mutations
C. Thymine dimers
D. Gene amplification
✅Answer: C
Rationale: UV light cross-links adjacent thymine bases, distorting DNA.
11. Fungi lacking observed sexual reproduction belong to which group?
A. Basidiomycetes
B. Deuteromycetes
C. Ascomycetes
D. Zygomycetes
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✅Answer: B
Rationale: Deuteromycetes = “imperfect fungi” because sexual forms are unknown.
12. A mass of fungal hyphae is called:
A. Thallus
B. Sporangium
C. Mycelium
D. Septum
✅Answer: C
Rationale: Hyphae collectively form a mycelium — the body of a fungus.
13. Which methods help identify and classify bacteria?
A. Only biochemical tests
B. Only nucleic acid tests
C. Microscopy, culture traits, biochemical tests, and nucleic acid analysis
D. Only Gram stain
✅Answer: C
Rationale: Modern taxonomy combines phenotypic and genotypic methods.
14. Lichens consist of:
A. Virus and fungus
B. Bacterium and fungus
C. Alga and fungus
D. Moss and fungus
✅Answer: C
Rationale: A fungal partner + a photosynthetic alga or cyanobacterium.
15. The terms yeast, mold, and mushroom refer to fungal:
