This set of Vector Biology Interview Questions and Answers for freshers focuses on “Vectors for Yeast – 2”.
1. What does the word episomal in YEps indicate?
a) Expression
b) Replication
c) Independent replication
d) Mutation
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Explanation: The word episomal in YEps indicates that it can replicate independently but also implies that integration into one of the yeast chromosomes can occur.
2. Why does the integration of YEp vector occur in a yeast chromosome?
a) Recombination
b) Smaller size
c) Similarity with host
d) Lytic cycle
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Explanation: The integration of YEp vector into the host chromosome of yeast may occur because the host contains a mutated copy of the same gene.
3. What is the role of homologous recombination in vector infection?
a) Integration
b) Host recognition
c) Duplication
d) Packaging
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Explanation: Homologous recombination occurs between the YEp vectors and the yeast chromosome. This occurs because the homologous genes are present on both the plasmid and the host chromosome.
4. In homologous recombination what part of the plasmid gets integrated into the host?
a) Origin part
b) Cos sites
c) Entire plasmid
d) Gene of interest
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Explanation: Homologous recombination can occur between plasmid gene and yeast mutant gene, resulting in the insertion of the entire plasmid.
5. What does “I” in Yips vectors stand for?
a) Infected
b) Integrative
c) Insertional
d) Initiation
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Explanation: Yeast Integrative Plasmids, YIPs are basically bacterial plasmids carrying a yeast gene. An example is Yip5.
6. Which gene does Yip5 carry?
a) LEU2
b) URA3
c) cI
d) Amp
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Explanation: Yeast integrative plasmid Yip5 is Pbr322 with an inserted URA3 gene, coding for decarboxylase enzyme which acts as a selectable marker.
7. What is the role of decarboxylase enzyme encoded by URA3 gene?
a) Nucleotide catalysis
b) Uracil formation
c) Leucine formation
d) Lactose breakdown
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Explanation: The URA3 gene codes for orotidine-5’-phosphate decarboxylase which is an enzyme that catalyzes one of the steps in the biosynthesis pathway for pyrimidine nucleotides.
8. A Yeast integrative plasmid cannot replicate as a plasmid inside the host?
a) True
b) False
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Explanation: A Yip cannot replicate as a plasmid as it does not contain any parts of the 2 micro-meter plasmid and instead depends on for its survival on integration into yeast chromosomal DNA.
9. What does “R” in YRP vector stand for?
a) Recombination
b) Replicative
c) Replication
d) Reverse combining
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Explanation: Yeast Replicative plasmids YRPs are able to multiply as independent plasmids because they carry a chromosomal DNA sequence that includes an origin of replication.
10. TRP1 gene is contained in which of the following?
a) YRP7
b) YIP2
c) YRP3
d) YIP3
View Answer
Explanation: YRP7 is an example of a replicative plasmid. It is made up of Pbr322 plus the yeast gene TRP1, located adjacent to the origin of replication.
11. What is the function of TRP1 gene?
a) Tryptophan biosynthesis
b) Tyrosine biosynthesis
c) Tetracycline biosynthesis
d) Termination
View Answer
Explanation: TRP1 is a yeast gene located adjacent to chromosomal origin of replication. It is involved in Tryptophan biosynthesis.
12. What does the yeast DNA fragment present in YRP7 consist of?
a) TRP1 and origin
b) TRP1 and gene of interest
c) TRP1 and cos sites
d) TRP1 and codons
View Answer
Explanation: TRP1 is a yeast gene located adjacent to chromosomal origin of replication. It is involved in Tryptophan biosynthesis.
13. Transformation frequency decides _________
a) Choice of host
b) Choice of vector
c) Choice of medium
d) Choice of temperature
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Explanation: Transformation frequency determines the efficiency of a yeast cloning vector and hence plays a major role in the choice of a vector.
14. Why is a high transformation frequency needed?
a) Large recombinants
b) Ease of infection
c) Host suitability
d) Easy scaleup
View Answer
Explanation: Transformation frequency is a measure of the number of transformants that can be obtained per microgram of plasmid DNA.
15. Which of the following have highest transformation efficiency?
a) YIP
b) YEP
c) YRP
d) YAC
View Answer
Explanation: Yeast episomal plasmids have the highest transformation frequency, providing between 10,000 and 100,000 transformed cells per microgram.
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