This set of 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
c) It can carry small DNA fragments
d) Origin of replication is taken from lambda
Explanation: 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
c) Single endonuclease digestion
d) Double endonuclease digestion
Explanation: 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?
c) Both non-recombinants and recombinants
d) Cells with self-ligated vectors
Explanation: 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
d) Hybrid vectors
Explanation: 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
c) Expressed genes
d) Protein products
Explanation: 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 Any desired gene can be withdrawn from the library and studied.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
c) Plasmid vectors
d) Cosmid vectors
Explanation: 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
c) E.coli genomic library construction
d) Stable transfection
Explanation: 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.
Explanation: 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
c) Plasmid vector
d) Phagemid vector
Explanation: 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?
Explanation: 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.
d) M13 bacteriophage
Explanation: 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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