Vector Biology Multiple Choice Questions on “Vectors for Yeast – 1”.
1. Why is a eukaryotic cloning vector required?
A. Cloning ease
B. Variety
A. Availability
D. Large scale production
Answer: D
Clarification: At times mere study of the gene is not the goal of a cloning experiment. Especially in biotechnology when the aim to obtain large amounts of product vectors and cell systems other than the prokaryotic ones are used.
2. Saccharomyces cerevisiae is an example of _________
A. Fungi
B. Yeast
A. Bacteria
D. Insect
Answer: B
Clarification: After the extensively used E.coli in the recombinant DNA technology, next comes S.cerevisiae which is a yeast and a eukaryotic organism.
3. Plasmids are present in eukaryotes.
A. True
B. False
Answer: A
Clarification: Plasmids are usually the extrachromosomal entities of a plasmid however a plasmid is also present in some strains of yeast.
4. The 2 micrometer circle found in yeast is a __________
A. Phage
B. Plasmid
A. Virus
D. Gene product
Answer: B
Clarification: The 2 micrometer circle found in yeast is the only plasmid of eukaryotic origin. The discovery of this plasmid has stimulated the use of yeast as a cloning vector.
5. What is the size of 2 micrometer circle?
A. 1 kb
B. 6 kb
A. 11 kb
D. 22 kb
Answer: B
Clarification: The 2 micrometer circle is approximately 6 kb in size, well within the range of an ideal vector. It is present in a yeast cell at a copy number of between 70 and 200.
6. What are REP1 and REP2 genes in the plasmid used for?
A. Origin
B. Replication
A. Expression
D. Host lysis
Answer: B
Clarification: Replication makes use of origin of replication, sever enzymes provided by the host and the REP1 and REP2 genes encoded by the plasmid.
7. Which selection system is used in a yeast plasmid recombinant?
A. Antibiotic
B. Lac
A. Auxotrophic mutant
D. cI gene
Answer: C
Clarification: A normal yeast gene which codes for an enzyme involved in amino acid biosynthesis is incorporated into the vector. The host that is selected has a mutated copy of the incorporated plasmid gene.
8. What is an auxotrophic mutant?
A. Defective plasmid
B. Transformed cell
A. Host cell
D. Yeast cell
Answer: C
Clarification: An auxotrophic mutant is a host cell that lacks or has a mutated copy of a gene coding for an enzyme involved in an essential amino acid biosynthesis.
9. What does the gene LEU2 code for?
A. Lactose
B. Leucine
A. Dehydrogenase
D. Hydrogenase
Answer: C
Clarification: LEU2 is a gene coding for the enzyme beta-isopropyl-malate-dehydrogenase, one of the enzymes involved in the conversion of pyruvic acid to leucine.
10. On which medium are yeast plasmids transformed cells plated?
A. Luria Broth
B. Agar
A. Minimal
D. Nutrient
Answer: C
Clarification: Minimal medium contains no added amino acids and therefore cells that produce all the amino acids can only grow. Transformed cells are only able to grow on minimal medium.
11. What are YEps?
A. Mutated yeast plasmids
B. Hybrid of yeast and bacteria
A. Yeast episomal plasmids
D. Transformed cells
Answer: C
Clarification: YEps are vectors derived from yeast plasmids. Some YEps contain the entire 2 micro-meter plasmids, others just include the origin of replication.
12. Yep13 is an example of _______
A. Yeast episomal plasmid
B. Host bacterium
A. Yeast integrative plasmid
D. Bacterial plasmid
Answer: A
Clarification: Yep13 is a yeast episomal plasmid derived from the 2 micro-meter plasmids. It includes only the original of replication from the parent plasmid.
13. What is a shuttle vector?
A. Hybrid vector
B. Mutated yeast plasmid
A. A vector that can be used with two/more systems
D. The transformed cell further used for transformation
Answer: C
Clarification: A shuttle vector is the one that can be used for transferring genetic material to more than one type of cells; essentially a eukaryotic and a prokaryotic system.
14. Yep13 is a shuttle vector.
A. True
B. False
Answer: A
Clarification: Yep13 includes the 2 micro-meter origin of replication, selectable LEU2 gene and the entire Pbr322 sequence. Hence it can be used for both yeast and E.coli.
15. For which of the following plasmids purification of a recombinant molecule from the transformed cell can be difficult?
A. Episomal plasmids
B. Integrative plasmids
A. Bacterial plasmid
D. All plasmids
Answer: B
Clarification: The yeast plasmid derived integrative plasmids are extremely difficult to purify from the host cell. These plasmids integrate into the host chromosome and remain their stable.