1. What additional feature does Pgem3Z has which makes it a suitable vector for in vitro transcription of cloned genes?
a) Unique Ori
b) Promoters
c) Clustered cloning sites
d) LacZ’ gene
Explanation: Pgem3Z has two promoters namely: T7 promoter and SP6 promoter; both being specific for the RNA Polymerase that is encoded by bacteriophage T7 and SP6.
2. The size of M13 phage vector is _________
a) 3 kb
b) 6.4 kb
c) 15.4 kb
d) 20.4 kb
Explanation: The genomic size of M13 bacteriophage is 6.4 kb which is bigger than most of the plasmid cloning vectors. Most of this length of M13 is taken up by ten closely placed genes.
3. There is a sequence region in M13 where the foreign DNA can be inserted. What is this sequence called?
a) Inverted repeat
b) Palindromic
c) Intergenic
d) Interstitial
Explanation: The intergenic sequence in M13 is 507 nucleotides long and is flanked by the genes IV and II. There are a total of 10 closely placed genes and this intergenic sequence.
4. The M13mp1 contains __________
a) LacZ’ gene
b) Ampicillin Resistance gene
c) Restriction sites
d) Tetracycline resistance gene
Explanation: The M13mp1 vector is constructed by incorporating LacZ’ gene in the intergenic sequence. This lacZ’ gene however does not harbor any restriction endonuclease site.
5. The M13mp2 consists ________ restriction site.
a) BamHI
b) AluI
c) PvuII
d) EcoRI
Explanation: This vector is a modification of M13mp1 and contains a unique restriction endonuclease site resulting from a mutation of GGATCC to GAATCC.
6. What is an additional feature of M13mp7?
a) 2 antibiotic resistance genes
b) Bigger size
c) Multiple cloning sites
d) Smaller size
Explanation: The M13mp7 contains multiple cloning sites all clustered into the polylinker and this polylinker is artificially synthesized and then inserted in the intergenic sequence.
7. What is a phagemid?
a) A hybrid vector
b) Phage vector
c) Plasmid vector
d) Viral vector
Explanation: Phagemid is a hybrid of M13 phage and Pbr322 plasmid. Pembl8 is an example of phagemid which was created by transferring into a pUC8 a 1300 bp fragment of M13 genome.
8. What does the M13 fragment in a phagemid contain?
a) BamHI restriction site
b) Signal sequences
c) Origin of replication
d) Promoter sequence
Explanation: These signal sequences are recognized by the enzymes that convert the normal double-stranded M13 molecule into single-stranded DNA before secretion of new phage particles.
9. Why is a helper phage needed when cloning experiments which a hybrid vector such as Pembl8 is done?
a) Efficient insertion
b) Attachment to host
c) To provide replicative enzymes
d) Stable transformation
Explanation: The hosts for Pembl8 cloning experiments are subsequently infected with a normal M13 to act as a helper phage, providing necessary replicative enzymes and phage coat proteins.
10. How can the recombinants of phagemid vector Pembl8 be identified?
a) Agar plating
b) Agar + Antibiotic
c) Agar + X-gal
d) Minimal media plating
Explanation: Pembl8, being derived from Puc8, has the polylinker cloning sites within the lacZ’ gene. So recombinants can be identified by the lac selection system.