Biology Test Biology Microbiology and Biotechnology 3 — Questions and Answers
Question 1: Which of the following is an example of horizontal gene transfer in bacteria?
- Binary fission
- Meiosis
- Conjugation (Correct answer)
- Mitosis
Correct answer: Conjugation
Conjugation is a form of horizontal gene transfer where a plasmid or chromosomal DNA passes from a donor to a recipient bacterium through a pilus.
Question 2: What is the primary purpose of a vector in recombinant DNA technology?
- To degrade foreign DNA in the host cell
- To carry and replicate foreign DNA in a host organism (Correct answer)
- To translate mRNA into protein
- To amplify RNA molecules
Correct answer: To carry and replicate foreign DNA in a host organism
A vector (e.g., plasmid or viral vector) carries recombinant DNA into a host cell and allows it to replicate and be expressed.
Question 3: Viruses that infect bacteria are specifically called:
- Retroviruses
- Bacteriophages (Correct answer)
- Prions
- Viroids
Correct answer: Bacteriophages
Bacteriophages (phages) are viruses that specifically infect bacterial cells and can follow lytic or lysogenic replication cycles.
Question 4: Which technique separates DNA fragments by size using an electric field?
- Southern blotting
- Gel electrophoresis (Correct answer)
- PCR
- DNA sequencing
Correct answer: Gel electrophoresis
Gel electrophoresis uses an electric field to migrate DNA through an agarose gel, with smaller fragments moving farther than larger ones.
Question 5: What is the main difference between gram-positive and gram-negative bacteria?
- Gram-negative bacteria have a thicker peptidoglycan layer
- Gram-positive bacteria have an outer lipopolysaccharide membrane
- Gram-negative bacteria have an outer membrane absent in gram-positive bacteria (Correct answer)
- Gram-positive bacteria lack a cell wall entirely
Correct answer: Gram-negative bacteria have an outer membrane absent in gram-positive bacteria
Gram-negative bacteria have an additional outer membrane containing lipopolysaccharides (LPS), which the Gram stain cannot penetrate, causing the cells to appear pink/red.
Question 6: In fermentation, what serves as the final electron acceptor?
- Oxygen
- NAD+
- An organic molecule (Correct answer)
- Carbon dioxide
Correct answer: An organic molecule
In fermentation, an organic molecule (such as pyruvate) serves as the final electron acceptor, regenerating NAD+ for continued glycolysis.
Question 7: Which component of a retrovirus is responsible for converting its RNA genome into DNA?
- RNA polymerase
- Reverse transcriptase (Correct answer)
- DNA ligase
- Helicase
Correct answer: Reverse transcriptase
Reverse transcriptase is the viral enzyme that synthesizes a DNA copy from the RNA genome of retroviruses such as HIV.
Biology Test Biology Microbiology and Biotechnology 3
Which of the following is an example of horizontal gene transfer in bacteria?