Chapter 2: Host Vector System — Online MCQ Test
BIOTECHNOLOGY · Grade 12 · CBSE(NCERT)
Practice Chapter 2: Host Vector System with a free chapter-wise online MCQ test.
This chapter covers: Host Organism Vector Plasmid Bacteriophage Artificial Chromosome Escherichia coli Yeast Gene Transfer Cloning Vector Transformation Recombinant DNA.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter 2: Host Vector System — Important Questions & Answers
In recombinant DNA technology, what is a vector?
- A. A DNA molecule used to carry a foreign DNA fragment into a host cell
- B. An enzyme that cuts DNA at specific sequences
- C. A host cell that produces restriction enzymes
- D. A protein that joins DNA fragments
Answer: A. A DNA molecule used to carry a foreign DNA fragment into a host cell
A vector acts as a carrier for introducing foreign DNA into a suitable host cell. Common examples include plasmids and bacteriophages.
A vector acts as a carrier for introducing foreign DNA into a suitable host cell. Common examples include plasmids and bacteriophages.
Which organism is most commonly used as a bacterial host in gene cloning experiments?
- A. Saccharomyces cerevisiae
- B. Escherichia coli
- C. Agrobacterium tumefaciens
- D. Neurospora crassa
Answer: B. Escherichia coli
Escherichia coli is widely used because it grows rapidly, is easy to manipulate, and has well-studied genetics.
Escherichia coli is widely used because it grows rapidly, is easy to manipulate, and has well-studied genetics.
A plasmid is best described as a:
- A. Linear RNA molecule found in viruses
- B. Circular extrachromosomal DNA molecule capable of replication
- C. Protein complex involved in DNA replication
- D. Part of the bacterial ribosome
Answer: B. Circular extrachromosomal DNA molecule capable of replication
Plasmids are usually circular, double-stranded DNA molecules present outside the bacterial chromosome. They can replicate independently.
Plasmids are usually circular, double-stranded DNA molecules present outside the bacterial chromosome. They can replicate independently.
What is the main role of a selectable marker in a cloning vector?
- A. To cut the vector DNA at a specific site
- B. To help identify cells that have taken up the vector
- C. To increase the size of the insert DNA
- D. To digest the host chromosome
Answer: B. To help identify cells that have taken up the vector
Selectable markers, such as antibiotic resistance genes, allow transformed cells to survive under selective conditions. Non-transformed cells fail to grow.
Selectable markers, such as antibiotic resistance genes, allow transformed cells to survive under selective conditions. Non-transformed cells fail to grow.
Which of the following is NOT an essential feature of a typical cloning vector?
- A. Origin of replication
- B. Selectable marker
- C. Cloning site
- D. Mitochondrial membrane
Answer: D. Mitochondrial membrane
A cloning vector requires an ori, selectable marker, and suitable restriction or cloning sites. A mitochondrial membrane is not a part of a cloning vector.
A cloning vector requires an ori, selectable marker, and suitable restriction or cloning sites. A mitochondrial membrane is not a part of a cloning vector.
A multiple cloning site in a vector is useful because it:
- A. Provides many unique restriction sites for insertion of foreign DNA
- B. Increases the antibiotic concentration in the medium
- C. Makes the host resistant to all viruses
- D. Destroys non-recombinant plasmids automatically
Answer: A. Provides many unique restriction sites for insertion of foreign DNA
A multiple cloning site contains several unique restriction enzyme recognition sequences. This gives flexibility in choosing enzymes for cloning.
A multiple cloning site contains several unique restriction enzyme recognition sequences. This gives flexibility in choosing enzymes for cloning.
Which of the following best compares plasmid vectors and bacteriophage vectors?
- A. Both always remain outside host cells and never replicate
- B. Plasmids usually enter by transformation, while phage vectors enter through infection
- C. Plasmids infect bacteria like viruses, while phages need heat shock
- D. Only plasmids can carry any foreign DNA; phages cannot
Answer: B. Plasmids usually enter by transformation, while phage vectors enter through infection
Plasmids are commonly introduced into competent cells by transformation. Bacteriophage vectors deliver DNA to bacterial cells through infection.
Plasmids are commonly introduced into competent cells by transformation. Bacteriophage vectors deliver DNA to bacterial cells through infection.
In blue-white screening using a vector with the lacZ alpha region, a white colony generally indicates that:
- A. The lacZ alpha gene is intact and no insert is present
- B. The lacZ alpha gene has been disrupted by foreign DNA
- C. The host cell has no plasmid at all but survives antibiotic selection
- D. The insert DNA has been completely degraded
Answer: B. The lacZ alpha gene has been disrupted by foreign DNA
Insertion of foreign DNA into the lacZ alpha region disrupts beta-galactosidase activity. Such recombinant colonies appear white on suitable indicator medium.
Insertion of foreign DNA into the lacZ alpha region disrupts beta-galactosidase activity. Such recombinant colonies appear white on suitable indicator medium.
In a pBR322-like vector, a recombinant plasmid has an insert within the tetracycline resistance gene while the ampicillin resistance gene is intact. After replica plating, which colony type should be selected as recombinant?
- A. Grows on ampicillin plate but fails to grow on tetracycline plate
- B. Fails to grow on both ampicillin and tetracycline plates
- C. Grows on tetracycline plate but fails to grow on ampicillin plate
- D. Grows equally well on both ampicillin and tetracycline plates
Answer: A. Grows on ampicillin plate but fails to grow on tetracycline plate
The intact ampR gene allows growth on ampicillin, but insertional inactivation of tetR prevents growth on tetracycline. This phenotype identifies recombinants.
The intact ampR gene allows growth on ampicillin, but insertional inactivation of tetR prevents growth on tetracycline. This phenotype identifies recombinants.
In a transformation experiment, 200 colonies are obtained after plating cells transformed with 10 ng of plasmid DNA. What is the transformation efficiency?
- A. 2 × 10^2 transformants per microgram DNA
- B. 2 × 10^3 transformants per microgram DNA
- C. 2 × 10^4 transformants per microgram DNA
- D. 2 × 10^5 transformants per microgram DNA
Answer: C. 2 × 10^4 transformants per microgram DNA
10 ng is 0.01 microgram. Transformation efficiency is 200 divided by 0.01, which equals 2 × 10^4 transformants per microgram DNA.
10 ng is 0.01 microgram. Transformation efficiency is 200 divided by 0.01, which equals 2 × 10^4 transformants per microgram DNA.