Vector Biology and Gene Manipulation Questions and Answers Part-16

1. Which gene does Yip5 carry?
a) LEU2
b) URA3
c) cI
d) Amp

Answer: b
Explanation: Yeast integrative plasmid Yip5 is Pbr322 with an inserted URA3 gene, coding for decarboxylase enzyme which acts as a selectable marker.

2. What is the role of decarboxylase enzyme encoded by URA3 gene?
a) Nucleotide catalysis
b) Uracil formation
c) Leucine formation
d) Lactose breakdown

Answer: a
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.

3. A Yeast integrative plasmid cannot replicate as a plasmid inside the host?
a) true
b) false

Answer: a
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.

4. What does “R” in YRP vector stand for?
a) Recombination
b) Replicative
c) Replication
d) Reverse combining

Answer: b
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.

5. TRP1 gene is contained in which of the following?
a) YRP7
b) YIP2
c) YRP3
d) YIP3

Answer: a
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.

6. What is the function of TRP1 gene?
a) Tryptophan biosynthesis
b) Tyrosine biosynthesis
c) Tetracycline biosynthesis
d) Termination

Answer: a
Explanation: TRP1 is a yeast gene located adjacent to chromosomal origin of replication. It is involved in Tryptophan biosynthesis.

7. 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

Answer: a
Explanation: TRP1 is a yeast gene located adjacent to chromosomal origin of replication. It is involved in Tryptophan biosynthesis.

8. Transformation frequency decides _________
a) Choice of host
b) Choice of vector
c) Choice of medium
d) Choice of temperature

Answer: b
Explanation: Transformation frequency determines the efficiency of a yeast cloning vector and hence plays a major role in the choice of a vector.

9. Why is a high transformation frequency needed?
a) Large recombinants
b) Ease of infection
c) Host suitability
d) Easy scaleup

Answer: a
Explanation: Transformation frequency is a measure of the number of transformants that can be obtained per microgram of plasmid DNA.

10. Which of the following have highest transformation efficiency?
a) YIP
b) YEP
c) YRP
d) YAC

Answer: b
Explanation: Yeast episomal plasmids have the highest transformation frequency, providing between 10,000 and 100,000 transformed cells per microgram.