Genetic Engineering test focuses on “BAC Vector, M13 and its Derivatives – 2”.
1. What is the size of the DNA molecule which can be packed by the viral protein coat?
a) 100kbp
b) 200kbp
c) 500kbp
d) No size restriction
Answer: d
Explanation: There is no size restriction on the DNA molecule which is packaged by the viral coat protein. It is an advantage.
2. The uniform layer of cells is known as lawn and the holes peppered from infected cells are termed as __________
a) plaques
b) holes
c) colony
d) pothole
Answer: a
Explanation: The infected cells, which are from the infection by bacteriophage create holes and they are termed as plaques.
3. M13 doesn’t actually lyse the cells.
a) True
b) False
Answer: a
Explanation: M13 doesn’t actually lyse the cells. It infects the cells and retards the growth but doesn’t actually lyse the cells.
4. The plaques formed by M13 infection are called as __________
a) retarded plaques
b) true plaques
c) pseudoplaques
d) lysogenized plaques
Answer: c
Explanation: As the plaques created by M13 are because of slow growth and not because of lysis, these plaques are called as pseudoplaques.
5. M13 vector is tightly packed. Where is the available site to insert DNA?
a) In the gene II
b) Between gene II and IV
c) Between gene III and V
d) Between gene V and VIII
Answer: b
Explanation: The production of phage depends upon the insertion of DNA without disrupting any of the phage genes. Hence, M13 vector is tightly packed. One such site for the insertion of DNA is between gene II and gene IV. Here, the lacZ and MCS are also present.
6. Choose the incorrect statement with respect to the collection of single stranded molecules.
a) An infected culture is set up and after a while the cells are removed by centrifugation
b) The phage is in the supernatant and is precipitated by addition of glycol and sodium chloride
c) The phage pellet is resuspended and phenol is used for removal of protein
d) The single stranded molecules sediment at the bottom
Answer: d
Explanation: The collection of single stranded molecules is slightly different. An infected culture is set up and after a while cells are removed by centrifugation. The phage is present in the supernatant and is precipitated by addition of glycol and sodium chloride. It is followed by centrifugation. The phage pellet is resuspended and phenol is used for removal of protein. The single stranded molecules remain in the solution and thus can be precipitated further.
7. Choose the correct statement for Sanger’s method of sequencing.
a) They are also called as chain termination methods
b) Use of M13 vector is made for getting double stranded DNA
c) Use of dideoxynucleotide phosphate (ddNTP) is made
d) The use of M13 vectors is more preferred these days
Answer: a
Explanation: Sanger’s method of DNA sequencing is also known as the chain termination method of sequencing. Dideoxynucleoside triphospahte (ddNTP) are used as chain terminating agents. M13 vector is used to obtain the single stranded DNA. Now a days there are technologies available for sequencing on double stranded DNA, thus it reduces the use of M13 vectors these days.
8. Which of the statement doesn’t holds for phage display systems?
a) The filamentous phage is often used as phage display system
b) Coding sequences are inserted in one of the protein coating genes
c) The most common protein coding genes are gene II or gene VIII
d) The inserted is expressed along with other protein coat genes
Answer: c
Explanation: The filamentous phage is often used as phage display system. The coding sequences are inserted in one of the protein coding genes and the most common protein coding genes are gene III and gene VIII. The insert is expressed along with other protein coat genes.
9. Choose the correct statement for the synthesis of RNA probe?
a) Double stranded DNA is only used for probe synthesis
b) Single stranded DNA can be used for probe synthesis
c) Probes are prepared for RNA transcripts which are specific for only particular strand
d) Probes are prepared for RNA transcripts which are specific for both the strands
Answer: b
Explanation: RNA probe can be synthesized by single stranded DNA. This single stranded DNA can be obtained from filamentous phage. Probes are prepared for RNA transcripts which are specific for either of the DNA strands.
10. M13-plasmid vectors are often used. Which of the following is not a feature for this?
a) They are known as phagemid, plage or phasmid
b) Replication takes place through the origin of replication of M13 derivatives only
c) Replication from M13 requires proteins to be provided by helper phage
d) Some of the examples of these types of the combination are pUC 118, 119 and 120
Answer: b
Explanation: M13-plasmid vector hybridization is often used and they are referred to as phagemid, phasmid or plage. Replication can take place either by the origin of replication of the plasmid or by the origin of replication of M13. Replication from M13 requires additional protein to be provided from helper phage. Single-stranded DNA is produced after replication and is packaged in a protein coat. Some of the examples of this type of hybridization are pUC 118, 119 and 120.
11. The main advantage of phagemid is that it can be used for the generation of single or double stranded products without recloning.
a) True
b) False
Answer: a
Explanation: The main advantage of pahgemid is that it can be used for the generation of single or double stranded products without recloning. It is so because M13 can be used to produce single stranded products and the double stranded products are obtained by using the origin of replication of plasmid.