MCQs on Cloning using a Simple Plasmid and Alpha Complementation – 1

1 - Question

Plasmids are used for carrying out the cloning procedure. Which of the statement is true for plasmids?
a) Bacterial plasmids are linear in nature
b) They are single stranded
c) Insertion of DNA into plasmid allows it to be propagated in host cells and they are known as vectors because of their this property
d) They are not capable of replication in bacteria
View Answer Answer: c
Explanation: Plasmids are double stranded and they are circular in nature. They are capable of replication in bacteria. Insertion of DNA into plasmid allows it to be propagated in host cells and the molecules which are used for propagation by this method are called as vectors.



2 - Question

Which of the following characteristic is not present in a plasmid on a general basis?
a) Multiple cloning site (MCS)
b) Origin of replication (ori)
c) Antibiotic resistance gene
d) Beta galactose genes
View Answer Answer: d
Explanation: Plasmid generally consists of characteristics such as multiple cloning site, origin of replication, antibiotic resistant genes and beta galactosidase genes. An origin of replication is necessary for the replication to take place.



3 - Question

Bla is a gene, which is incorrect for it?
a) It is an antibiotic resistance genes
b) Antibiotic acts by blocking the cross-linking of the bacterial cell wall and thus leading to lysing of cells
c) It encodes beta lactamase enzyme
d) The beta lactam ring is activated
View Answer Answer: d
Explanation: Bla is an ampicillin resistant gene. Antibiotic acts by blocking the cross-linking in the bacterial cell wall and thus leading to lysing of the cells. If antibiotic resistant gene is used, which encodes for beta lactamase enzyme it inactivates the beta lactam gene by hydrolysing it.



4 - Question

Which of the characteristics is present in lacZ gene?
a) It encodes for beta galactosidase enzyme
b) Beta galactosidase enzyme is responsible for cleaving monosaccharides into the constituent elements
c) It doesn’t cleaves a substrate called as X-gal
d) But if X-gal is cleaved, it liberates pink coloured dye
View Answer Answer: a
Explanation: lacZ gene encodes for beta galactosidase enzyme. This enzyme is responsible for cleaving of disaccharides into monosaccharides. It cleaves a substrate known as X-gal, which then liberates a blue dye.



5 - Question

Which of the following orientation is not propagated to later stages?
a) Circular plasmids having genomic DNA
b) Intramolecular ligation of plasmids
c) Linear molecules
d) Head to head ligation of two DNA plasmids
View Answer Answer: c
Explanation: When a cloning experiment is carried out, there various orientations which are possible. The orientation which is not propagated to the later stages is a linear molecule. Other possible orientations are relegation of plasmid, intramolecular ligation of genomic DNA. Intermolecular ligation of two DNA plasmids and genomic plasmids is also possible.



6 - Question

Molecules having new combination of sequences that were not present before are called as __________
a) intermolecular ligants
b) recombinants
c) couple
d) intramolecular ligants
View Answer Answer: b
Explanation: After cloning experiment is carried out, there are various orientations possible. Molecules having combination of new sequences which were not present earlier are called as recombinants.



7 - Question

Insertion of DNA into lacZ gene may lead to disruption of the gene function
a) True
b) False
View Answer Answer: a
Explanation: Insertion of DNA into lacZ gene may lead to disruption of the gene function. It always doesn’t so but there are minimal chances that function is not disrupted because often it leads to shifting of the reading frame.



8 - Question

Transformation efficiency is defined as __________
a) ratio of transformed colonies by microgram of sample DNA that is to be inserted
b) ratio of transformed colonies by amount of sample DNA that is to be inserted
c) ratio of transformed colonies by microgram of plasmid DNA
d) ratio of transformed colonies by amount of plasmid DNA
View Answer Answer: d
Explanation: Transformation efficiency is defined as the ratio of transformed colonies to that of the amount of plasmid DNA which is taken. It is often altered by altering the competence of the cells.



9 - Question

After carrying out the cloning experiment, the cells are plated on agar. Along with agar, it also contains antibiotic resistant genes, X-gal and an inducer of lacZ gene. Which of the following would grow?
a) Cells that have taken up plasmid DNA
b) Cells that have taken up genomic DNA
c) Cells having no insert
d) Cells either having no insert or having genomic DNA
View Answer Answer: a
Explanation: Only cells that have taken up the plasmid DNA would be able to grow. It is so because the only plasmid is having antibiotic resistant genes and the rest will die after a few generations.

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