Category: Vector Biology Objective Questions

Vector Biology Multiple Choice Questions on “Vectors for Mammals – 7”.

1. In the case of helper-dependent viral vectors, what does the helper virus contain?
A. Homeotic genes
B. Origin
A. Transposon
D. Missing genes
Answer: D
Clarification: If the insertion of transgene replaces an essential viral gene, the vector is rendered helper dependent. A helper virus is then co-introduced which carries the missing genes.

2. Usage of “packaging lines” is an alternative to __________
A. Cloning
B. Recombination
A. Co-introduction of helper virus
D. Viral vector for gene transfer
Answer: C
Clarification: An alternative to the co-introduction of helpers is to use a complementary cell line, sometimes termed as a packaging line, which is transformed with the appropriate missing genes.

3. What are amplicons?
A. Gut-less vectors
B. Hybrid vectors
A. Helper virus
D. Helper phage
Answer: A
Clarification: The amplicons are fully deleted, gutted or gutless vectors that contain just the cis-acting elements required for packaging and genome replication.

4. Which element in the amplicons is responsible for packaging?
A. Trans
B. Cis
A. Amp
D. Cysteine
Answer: B
Clarification: The amplicons are fully deleted, gutted or gutless vectors that contain just the cis-acting elements required for packaging and genome replication.

5. The advantage of “gutless vectors” is that they possess no intrinsic cytotoxic effects.
A. True
B. False
Answer: A
Clarification: The advantage of such vectors is their high capacity for foreign DNA and the fact that, since no viral gene products are made, the vector has no intrinsic cytotoxic effects.

6. Which of the following is an example of rod-shaped virus?
A. Baculovirus
B. Papillomavirus
A. Adenovirus
D. Retrovirus
Answer: A
Clarification: Rod-shaped viruses such as baculoviruses form the capsid around the genome, so there are no such size constraints.

7. Retrovirus is an example of ____________ virus.
A. Plant
B. Icosahedral
A. Hybrid
D. Binary
Answer: B
Clarification: Icosahedral virus Adenovirus and Retrovirus package their genomes into preformed capsids, whose volume defines the maximum amount of foreign DNA that can be accommodated.

8. Adenovirus vectors are useful for short-term transgene expression because _____________
A. Inefficient integration
B. Efficient integration
A. High stability
D. Small size
Answer: A
Clarification: Adenovirus vectors are suitable for transient expression in dividing cells because they do not integrate efficiently into the genome.

9. Adenovirus vectors can be used for ___________ cells such as neurons.
A. Somatic
B. Germ
A. Totipotent
D. Post-mitotic
Answer: D
Clarification: Adenovirus vectors are suitable for transient expression in dividing cells because they do not integrate efficiently into the genome, but prolonged expression can be achieved in post-mitotic cells such as neurons.

10. Adenovirus-derived vaccines have been used in humans with no reported side-effects.
A. True
B. False
Answer: A
Clarification: Adenoviruses are particularly attractive as gene therapy vectors because the virions are taken up efficiently by the cells in vivo and adeno-virus derived vaccines have been used in humans with no reported side-effects.

11. The deletion of which genes in an Adenovirus vector precludes the immunological effects?
A. E7
B. E2
A. E3
D. E4
Answer: D
Clarification: The use of E1 or E4 deletions is particularly attractive as the E4 gene is responsible for many of the immunological effects of the virus.

12. Insertion of stuffer DNA into which of the gene keeps recombination from happening?
A. E1
B. E2
A. E3
D. E4
Answer: C
Clarification: Insertion of stuffer DNA into the non-essential E3 gene can be done so that recombination yields a genome too large to be packaged.

13. Adeno-associated Virus was actually first discovered as a ___________
A. Contaminant
B. Human virus
A. Insect virus
D. Phage
Answer: A
Clarification: Adeno-associated virus (AAV) is not related to Adenovirus, but is so called because it was first discovered as a contaminant in the adenoviral state.

14. AAV is naturally __________
A. Translation defective
B. Replication defective
A. Small in size
D. Lacking attachment ability
Answer: B
Clarification: Adeno-associated virus is a single-stranded DNA virus, a member of the parvovirus family, and is naturally replication defective.

15. What happens to the AAV DNA in the absence of helper virus?
A. Does not infect the cell
B. Does not integrate
A. Integrates into host genome
D. Cannot synthesize proteins
Answer: C
Clarification: In the absence of helper virus vectors, the AAV DNA integrates into host cell’s genome, where it remains as a latent provirus.

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Vector Biology Multiple Choice Questions on “Cloning Vectors Based on Phages”.

1. To which organism does bacteriophage lambda belong?
A. Pseudomonas
B. Bacillus subtilis
A. Escherichia coli
D. Saccharomyces cerevisiae
Answer: C
Clarification: Bacteriophage lambda is genetically complex but very extensively studied virus of E.coli. Because it has been the object of so much research in molecular genetics, it was natural that, right from the beginnings.

2. What is the confirmation of lambda phage DNA when it is isolated from the phage particle?
A. Supercoiled
B. Open circular
A. Linear
D. Linear duplex
Answer: B
Clarification: The phage DNA molecule, unlike the bacterial plasmid DNA, exists usually in a linear conformation and DNA is a duplex molecule.

3. Who determined the sequence of Lambda phage?
A. Sanger
B. Maxam Gilbert
A. Ramachandran
D. John Williams
Answer: A
Clarification: The exact sequencing of lambda phage of 49 kb was done with Sanger sequencing method in 1982. The principle of the method was chain termination.

4. What form does the phage DNA take when it is injected into the host?
A. Linear
B. Circular
A. Double helical
D. Supercoiled
Answer: B
Clarification: There are 12 bp long overhangs present at each end of the phage DNA which are complementary to each other and result in its circularization upon insertion into the host.

5. Which region of the phage genome is not essential for growth?
A. Between N and Q genes
B. Cohesive sites
A. Recombination and lysogenization
D. Host lysis
Answer: C
Clarification: The recombination and lysogenization region are non-essential for the growth of phage inside the host molecule. This region hence can be replaced with foreign DNA.

6. What is the role of phage cI gene?
A. Host lysis
B. Dormancy and immunity
A. Gene regulation
D. Temperature regulation
Answer: B
Clarification: A phage may convert to a dormant lifestyle inside the host that is switching to becoming a prophage rather than causing a lytic infection. The product of the phage cI gene is responsible for conferring dormancy and immunity to superinfection.

7. What is the function of early gene regulation?
A. Replication
B. Recombination
A. Lytic cycle
D. Cohesive site formation
Answer: C
Clarification: The early gene transcription establishes the lytic cycle in competition with lysogeny. In the lytic cycle, lambda transcription occurs in three phases.

8. What is the function of late gene regulation?
A. Packaging DNA
B. Host lysis
A. Host infection
D. Replication
Answer: A
Clarification: In the lambda lytic cycle there are three temporal stages: early, middle and late. Late is responsible for packaging the DNA into mature phage particles.

9. The cI gene is of what type?
A. Inducer
B. Promoter
A. Repressor
D. Silent gene
Answer: C
Clarification: The cI gene is a repressor gene. Following infection, early transcription proceeds from major promoters situated to the left and right of the cI gene.

10. What is the role of N and Q genes?
A. Positive regulation
B. Negative regulation
A. Transcription initiation
D. Transcription termination
Answer: A
Clarification: Both N and Q pay positive regulatory roles essential for phage growth and plaque formation. But an N-negative phage can produce a small plaque if the termination site is removed.

11. When was bacteriophage discovered?
A. 1915-1917
B. 1980
A. 1819-1821
D. 2000
Answer: A
Clarification: Virus that infects bacteria is known as a phage and was discovered by Fredrick in Britain (1915) and Felix in France (1917).

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Gene Manipulation Questions and Answers for Entrance exams focuses on “Gene Manipulation in Gram – Negative Bacteria”.

1. What is required to clone DNA in non-enteric bacteria?
A. Enzymes
B. PCR
A. Plasmid
D. Phage
Answer: C
Clarification: For cloning in non-enteric bacteria, bacteria other than E. coli, a plasmid cloning vector is required which can replicate in the selected organism.

2. In Gram-negative bacteria other than E.coli, it is used as a ___________
A. Hybrid vector
B. Main host
A. Inhibitor
D. Intermediate host
Answer: D
Clarification: Under normal circumstances, E.coli is used as an intermediate host for a transformation of the ligation mix and screening of the recombinants.

3. The vector used for cloning in non-enteric bacteria must also be able to replicate in E.coli.
A. True
B. False
Answer: A
Clarification: Since E. coli is used as an intermediate host in cloning of the non-enteric bacteria, the vector used must also be able to replicate in E. coli.

4. If the selectable markers are not expressed in the new host, then ____________ is necessary.
A. Helper phage
B. Manipulations
A. Temperature control
D. Recombination
Answer: B
Clarification: If the selectable markers are not expressed in the new host, then extensive manipulations may be necessary to enable detection of transformants.

5. RSF1010 specifies resistance to how many antimicrobial agents?
A. 1
B. 2
A. 3
D. 4
Answer: B
Clarification: Plasmid RSF1010 is a multicopy replicon which specifies resistance to two antimicrobial agents, sulfonamide and streptomycin.

6. What is the length of DNA of RSF1010?
A. 4684 bp
B. 6684 bp
A. 7684 bp
D. 8684 bp
Answer: D
Clarification: The plasmid DNA of RSF1010 is 8684 base pairs in length and has been completely sequenced. A detail physical and functional map has been constructed.

7. How many PstI sites in plasmid RSF1010?
A. 1
B. 2
A. 3
D. 4
Answer: B
Clarification: There are two PstI sites in RSF1010, about 750 base pairs apart, which flank the sulfonamide resistance determinant. PstI is a restriction enzyme.

8. How many unique cleavage sites are located within the antibiotic resistance determinants of plasmid RSF1010?
A. 0
B. 2
A. 4
D. 6
Answer: A
Clarification: None of the unique cleavage sites is located within the antibiotic resistance determinants and none is particularly useful for cloning.

9. Insertion of DNA fragment between PstI sites ____________ the resistance determinant.
A. Activates
B. Inactivates
A. Weakens
D. Removes
Answer: B
Clarification: Insertion of DNA fragment between the PstI sites inactivates both the antibiotic resistance determinants. Hence a new selectable marker has to be used.

10. Which resistance is lost if DNA is inserted in EcoR1 or BstEII sites?
A. Sulphonamide
B. Alcohol
A. Ampicillin
D. Streptomycin
Answer: D
Clarification: Although the sites EcoR1 and BstII lie outside the coding regions of the gene, streptomycin resistance is lost if a DNA fragment is inserted at these sites.

11. What is the size of IncP alpha plasmids?
A. 20 kb
B. 40 kb
A. 60 kb
D. 80 kb
Answer: C
Clarification: The IncP alpha plasmids: R18, R68, RK2, RP1 and RP4 are 60 kilobases in size and their genomes have been completely sequenced.

12. IncP alpha plasmids are smaller in size than IncPbeta plasmids.
A. True
B. False
Answer: B
Clarification: The IncP alpha plasmids are 60 kilobases in size whereas IncP beta plasmids are 52 kilobases in size. Both have been developed as conjugative vectors.

13. IncP alpha and InP beta are _________ host range vectors.
A. Overlapping
B. Narrow
A. Broad
D. Specific
Answer: C
Clarification: Mini versions of the IncP-group plasmids such as IncP alpha and IncP beta have been developed as conjugative broad host range vectors.

14. P-group plasmids are not widely used as vectors because of their _____________
A. Big size
B. Small size
A. Toxicity
D. Host range
Answer: A
Clarification: Much is known about the genome of P-group plasmids such as their restriction site locations and genes carried. Despite this, they are not widely used as vectors because of their large size which makes manipulations difficult.

15. Blanty’s group of mini-IncP plasmids has a maximum size of _______ kb.
A. 1
B. 3
A. 5
D. 7
Answer: D
Clarification: Blanty’s group of mini-IncP plasmids as vectors was created in 1997. Their vectors are only 4.8 to 7.1 kb in size but can still be maintained in a wide range of gram-negative bacteria.

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Advanced Vector Biology Questions and Answers focuses on “Vectors and Cloning in Gram – Positive Bacteria – 3”.

1. The promoters of B. subtilis vectors have conserved polyA and ________ tails.
A. PolyT
B. PolyC
A. PolyG
D. PolyA
Answer: A
Clarification: The promoters also have conserved polyA and polyT tracts upstream of the -35 region. Some promoters also have a -16 region.

2. Ribosomes from _________ recognize only homologous mRNA.
A. E. coli
B. B. subtilis
A. Yeast
D. Bacteriocins
Answer: B
Clarification: E. coli ribosomes can support protein synthesis when directed by mRNA from a range of Gram-positive and Gram-negative organisms, whereas Ribosomes from B. subtilis recognize only homologous mRNA.

3. The selectivity of ribosomes of B. subtilis is due to the lack of ________
A. Inducer
B. Promoter
A. Protein S1
D. Repressor
Answer: C
Clarification: Ribosomes from B. subtilis recognize only homologous MRNA. This is because they lack a counterpart of the largest E. coli Ribosomal protein.

4. Which of the following does not lack MRNA selectivity?
A. Streptococcus
B. Clostridium
A. E. coli
D. Lactobacillus
Answer: C
Clarification: Few gram-positive bacteria such as staphylococcus, streptococcus, clostridium, and lactobacillus, lack S1-equivalent E.coli protein and therefore exhibit MRNA selectivity.

5. The role of S1 is to bind ________ non-specifically.
A. MRNA
B. RNA
A. DNA
D. CDNA
Answer: B
Clarification: The role of S1 is to bind RNA non-specifically and bring it to the decoding site of the 30S subunit, where proper positioning of the Shine-Dalgarno sequence and initiation codon signals can take place.

6. When was the Spac system for low-GC hosts developed?
A. 1990
B. 1984
A. 1963
D. 1936
Answer: B
Clarification: The first controlled expression system to be used in B. subtilis was the Spac system, developed by Yansura and Henner in 1984.

7. Which gene of E. coli is contained in the Spac system?
A. Tol
B. Amp
A. LacI
D. Gal
Answer: C
Clarification: The first controlled expression system to be used in B. subtilis was the Spac system. This consists of the E. coli lacI gene and the promoter of phage SPO-1.

8. A promoter from which phage is incorporated in the Spac system?
A. Lambda
B. M13
A. Prophage
D. SPO-1
Answer: D
Clarification: The first controlled expression system to be used in B. subtilis was the Spac system. This consists of the E. coli lacI gene and the promoter of phage SPO-1.

9. E. coli T7 system is successfully implemented in B. subtilis.
A. True
B. False
Answer: A
Clarification: E. coli T7 system is implemented in B. subtilis by inserting the T7 RNA polymerase gene into the chromosome under the control of the Xylose-inducible promoter and cloning the gene of interest, coupled to T7 promoter, on a B. subtilis vector.

10. The promoter used in T7 system is inducible by which of the following?
A. Xylose
B. Galactose
A. Lactose
D. Fructose
Answer: A
Clarification: E. coli T7 system is implemented in B. subtilis by inserting the T7 RNA polymerase gene into the chromosome under the control of the Xylose-inducible promoter and cloning the gene of interest, coupled to T7 promoter, on a B. subtilis vector.

11. Expression of a heterologous gene in the T7 system is ____________
A. Easy
B. Difficult
A. Not possible
D. Costly
Answer: A
Clarification: Expression of a heterologous gene in the T7 expression system can be made simpler by putting it directly under the control of the promoter.

12. Other than B. subtilis, the T7 expression system can also be used in __________
A. Lactobacillus
B. Yeast
A. Fungi
D. Agrobacterium
Answer: A
Clarification: A xylose inducible system has also been developed in lactobacillus and staphylococci. Many different controllable promoters are available.

13. In the phi-31 system of L. lactis, _________ vector is used.
A. Hybrid
B. Mammalian
A. Low copy number
D. High copy number
Answer: C
Clarification: In the phi-31 system of L. lactis, the gene of interest is placed under the control of a phage middle promoter inserted in a low copy number vector carrying the phage region ori.

14. In the phi-31 system of L. lactis, gene of interest is placed under the control of _____________ promoter.
A. Weak
B. Strong
A. End
D. Middle
Answer: D
Clarification: In the phi-31 system of L. lactis, the gene of interest is placed under the control of a phage middle promoter inserted in a low copy number vector carrying the phage region ori.

15. Following infection with phi-31, __________ increases.
A. Copy number
B. Mortality rate
A. Size
D. Protein production
Answer: A
Clarification: Following infection of the host cell with phi-31, the plasmid copy number rapidly increases and this is followed by expression from the phage promoter.

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Vector Biology Assessment Questions and Answers focuses on “Vectors for Mammals – 6”.

1. Agrobacterium tumefaciens can transfer DNA to animal cells.
A. True
B. False
Answer: A
Clarification: A. tumefaciens and its close relatives have been used for over 20 years to generate transgenic plants. More recently, it has been shown that A. tumefaciens can transfer DNA to cultured human cells.

2. Which of the following is an artificial form of bactofection?
A. Transduction
B. Protoplast fusion
A. Bolistics
D. Electroporation
Answer: B
Clarification: The protoplast fusion technique can be regarded as a highly artificial form of bactofection, but the amount of human intervention required distinguishes the technique.

3. In the cases of Salmonella species, lysis occurs in the __________
A. Outside the phagocytic vesicle
B. Inside the phagocytic vesicle
A. In lymphatic system
D. In nucleus
Answer: B
Clarification: In the case of Salmonella species, lysis occurs in the phagocytic vesicle, while for other species lysis occurs after the bacterium has escaped from the vesicle.

4. Which of the following occurs in DNA transfer by A. Tumefaciens?
A. Cell lysis
B. Conjugation
A. Infection
D. Myeloma
Answer: B
Clarification: A. tumefaciens transfers DNA to mammalian cells without invading them. Transfer occurs by attachment to the outside of the cell followed by conjugation.

5. Pilus helps in the transfer of DNA through a process of ___________
A. Transduction
B. Transfection
A. Conjugation
D. Transformation
Answer: C
Clarification: In A. tumefaciens, transfer occurs by attachment to the outside of the cell followed by conjugation. It is a process of transfer of DNA through a conduit called a pilus, which is assembled by the bacterial cell.

6. Which is an important principle in gene transfer using live bacteria?
A. Amplification
B. Attenuation
A. Lysis
D. Phagocytosis
Answer: B
Clarification: An important principle in the use of live bacteria as invasive gene-transfer vehicles is that they must be attenuated.

7. What would happen if attenuated bacteria are not used for mammalian gene transfer?
A. Cell death
B. Tumor
A. Proliferation
D. Unsuccessful gene transfer
Answer: A
Clarification: The gene transfer system exploits the natural ability of the bacteria to infect and subvert the activity of eukaryotic cells. Without attenuation, the bacteria would multiply and destroy the host cells.

8. Which of the following is a technique of bacterial attenuation?
A. Auxotrophic mutants
B. Removal of cell wall
A. Protoplast fusion
D. Conjugation
Answer: A
Clarification: Attenuation is achieved in several ways. One way is to use auxotrophic mutants that are bacterial strains that are unable to manufacture essential molecules.

9. AroA mutants are unable to synthesize _____________
A. Amino acids
B. Homeotic genes
A. Vitamins
D. Aromatic compounds
Answer: D
Clarification: AroA mutants are unable to synthesize aromatic amino acids and Salmonella typhimurium and Shigella flexneri strains carrying this mutation have been used for gene transfer.

10. Inducible autolysis is a technique for attenuation.
A. True
B. False
Answer: A
Clarification: The bacteria can be engineered so that they undergo inducible autolysis. Attenuation can be achieved by induced suicide, introducing an autolysin-encoding gene that is activated once the bacterium is inside the host cell.

11. Attenuation of ‘Listeria Monocytogenes’ can be achieved by ___________
A. Auxotrophic strains
B. Autolysis
A. Gene knockout
D. Mutation
Answer: B
Clarification: There are no auxotrophic strains of Listeria monocytogenes, so attenuation is achieved by induced suicide. Autolysin-encoding gene is introduced.

12. Apart from the introduction of DNA into cultured cells, bacteria mediated gene transfer has also been used for ________
A. Recombinant protein production
B. Transgenic animal
A. In vivo gene transfer
D. In vitro gene transfer
Answer: C
Clarification: Bacteria mediated gene transfer has been used not only as general transfection method for the introduction of DNA into cultured cells but also as a high efficiency method for gene transfer in vivo.

13. Virus particles have a natural ability of ___________
A. Adsorbing on the cell surface
B. Proliferation
A. Inducing tumor
D. Inducing apoptosis
Answer: A
Clarification: Virus particles have a natural ability to adsorb to the surface of cells and gain entry, and this can be exploited to deliver recombinant DNA into animal cells.

14. Helper-independent vectors can _____________
A. Not Propagate
B. Propagate dependently
A. Propagate independently
D. Transduce the cell
Answer: C
Clarification: If the transgene is added to the genome, or if it replaces one or more genes that are non-essential for the infection cycle in the expression host being used, the vector is described as helper-independent because it can propagate independently.

15. What happens if an essential gene is replaced in a viral vector?
A. Helper dependent
B. Helper independent
A. Non-function
D. Loss of transfection ability
Answer: A
Clarification: If the transgene replaces an essential viral gene, this renders the vector helper-dependent so that missing functions must be supplied in trans.

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Vector Biology Questions and Answers for Freshers focuses on “Cloning Vectors for E.Coli – 4”.

1. Which of the following assertions is true in regard to a cosmid vector?
A. No plaques are produced
B. Lac-selection system is used
A. It can carry small DNA fragments
D. Origin of replication is taken from lambda
Answer: A
Clarification: The cosmid is a hybrid between lambda phage and a plasmid and only the cos sites in the whole construct of cosmid belong to the phage. Ampicillin and tetracycline resistance genes are taken from the plasmid, no plaque formation is observed.

2. What digestion pattern of the restriction endonucleases is followed while constructing recombinant molecule using a cosmid?
A. Partial digestion
B. Complete digestion
A. Single endonuclease digestion
D. Double endonuclease digestion
Answer: A
Clarification: Partial digestion of the cosmid vector molecules is done because total digestion will lead to small sized fragments which in turn will lead to difficulty in in-vitro packaging.

3. If cosmid vector infected cells are grown on an agar plate containing antibiotic, what type of colonies will grow?
A. Non-recombinants
B. Recombinants
A. Both non-recombinants and recombinants
D. Cells with self-ligated vectors
Answer: B
Clarification: Plating cosmid infected cells on agar and antibiotic plate will only give rise to recombinant colonies as only they possess the antibiotic resistance. Also, the non-recombinants will be too small to package into the phage coat.

4. Which vectors carry the longest foreign DNA fragments?
A. M13 based vectors
B. Lambda based vectors
A. Plasmids
D. Hybrid vectors
Answer: B
Clarification: The main use of all lambda based vectors is to clone DNA fragments that are too long to be handled by plasmid or M13 vectors. Lambda based vectors can take upto 40 kb of DNA.

5. What does an E.Coli genomic library contain?
A. Recombinant clones of genes
B. Genes in E.coli genome
A. Expressed genes
D. Protein products
Answer: A
Clarification: A genomic library is a set of recombinant clones that contains all of the DNA of the E.coli genome. Any desired gene can be withdrawn from the library and studied.

6. Which vectors are mostly used for creating genomic libraries?
A. Lambda phage vectors
B. M13 phage vectors
A. Plasmid vectors
D. Cosmid vectors
Answer: A
Clarification: Lambda phage vectors are the most suitable for creation of genomic libraries for E.coli and other prokaryotes because they can carry larger lengths of DNA fragments.

7. What is the main use of a Bacterial Artificial Chromosome (BAC. vectors?
A. E.coli protein expression
B. Human genomic library construction
A. E.coli genomic library construction
D. Stable transfection
Answer: B
Clarification: BAC vectors are specifically created to handle longer DNA inserts for the construction of human genomic libraries. BACs can handle inserts upto 300 kb in size, reducing the library size to just 30,000 clones.

8. BAC vectors are based on _________ plasmid.
A. R
B. F
A. Col
D. Trp
Answer: B
Clarification: BAC vectors are based on F plasmids which are the fertility plasmids responsible for the occurrence of genetic material transfer between two cells by means of conjugation. These are relatively large and have a higher capacity.

9. What are PACs?
A. Low capacity phage vector
B. High capacity phage vector
A. Plasmid vector
D. Phagemid vector
Answer: B
Clarification: P1 derived artificial chromosomes (PACs) are high capacity vectors that combine the features of P1 vectors and BAC vectors having a capacity of up to 300 kb.

10. Which type of vector is P1?
A. Phage
B. Plasmid
A. Cosmid
D. Phagemid
Answer: A
Clarification: P1 is a high capacity vector constructed from P1, which has the advantage over lambda of being able to squeeze 110 kb of DNA into its capsid structure.

11. Pjb8 is an example of __________ vector.
A. Cosmid
B. Phagemid
A. Hybrid
D. M13 bacteriophage
Answer: A
Clarification: Pjb8 is a cosmid vector constructed as a hybrid between a phage DNA molecule and a bacterial plasmid. Cos sites belong to the phage genome and all other genetic elements come from a plasmid.

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