This set of Vector Biology Multiple Choice Questions & Answers (MCQs) focuses on “Insertion and Replacement Vectors”.
1. Insertional and replacement vectors are types of ________ vector.
Explanation: Wild-type lambda DNA contains several target sites for most of the commonly used restriction endonucleases and so it is not suitable as a vector.
2. Multiple target sites in which foreign DNA can be inserted are present in an Insertion vector.
Explanation: Derivatives of the wild-type lambda phage are prepared that either has a single target site for the insertion of DNA called the insertion vectors; or have multiple cloning sites defining a fragment that can be replaced.
3. What modifications are done to the phage vector for creating derivative vectors?
a) Origin replacement
c) Antibiotic resistance incorporated
Explanation: Since the lambda phage can accommodate only about 5% more than its normal complement of DNA, vector derivatives are constructed with deletions to increase the space within the genome.
4. The maximum capacity of phage lambda vector is attained by _______ vectors.
Explanation: There is a stuffer fragment in the replacement vectors which can be replaced with foreign DNA. It contains multiple restriction sites.
5. The shortest lambda DNA molecules that produce plaques are _______ deleted.
Explanation: If a too much non-essential region is deleted from the genome, it cannot be packaged into phage particles efficiently.
6. Why is 64-69% of genomic region included in the stuffer fragment of replacement vectors?
a) Spi positive selection
b) Spi negative selection
c) Antibiotic selection
Explanation: The 64-69% of the lambda genomic region produce products that are responsible for inhibition of growth of lambda vector in a P2 lysogen infected cells.
7. What is the size of foreign DNA that can be inserted in an insertion vector?
a) 10 kb
c) 20 kb
d) 15 kb
Explanation: Packaging requirements limit the size of inserted foreign DNA fragments to 0 to 10 kb due to the limitation on viral genome size.
8. How can the unwanted restriction sites be removed?
Explanation: Removal of unwanted sites involves mutagenesis of phage restriction/modification systems.
9. The negative transcriptional vector in an insertion or replacement vector is __________
a) Ampicillin resistance
b) cI gene product
c) Tetracycline resistance
d) Kanamycin resistance
Explanation: The phage genome chooses between positive and negative regulators during the immediate early phase of the life cycle.
10. What are Hfl strains?
a) Morphology based strains
b) Homology based strains
c) Frequency based strains
d) Resistance based strains
Explanation: Hfl is the high frequency lysogeny strains which affect the lambda lysogenic-lytic decision. The resultant strains are 99.9% lysogenic and 0.1% lytic.
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