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Directions : In the following questions a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as :
Assertion (A) : β-galactosidase coding sequence acts as a selectable marker.
Reason (R) : Enzyme galactosidase converts the galactose into lactose.
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Galactosidase is an enzyme that converts the galactose into lactose. This property makes this enzyme to be used as a selectable marker or reporter gene in molecular biology experiments. This property is exploited during the selection of recombinants from the non-recombinants.
Assertion (A) : DNA is a positively charged molecule.
Reason (R) : DNA moves towards the positive electrode (anode).
DNA is a negatively charged molecule, hence it moves towards the positive electrode (anode).
Assertion (A) : Thermus aquaticus, is used in PCR technique.
Reason (R) : It is a heat-stable DNA polymerase.
Thermus aquaticus is the source of DNA polymerase because it is a heat-stable DNA polymerase.
Assertion (A) : E. coli having pBR322 with DNA insert at BamHI site cannot grow in medium containing tetracycline.
Reason(R) : Recognition site for BamH I is present in TetR region of pBR322.
pBR322 carries recognition sites for a number of commonly used restriction enzymes. Recognition site for BamHl is present in the tetr region i.e., the region responsible for tetracycline resistance. When an insert is added at the BamHl recognition site the gene for tetracycline resistance becomes non-functional and the recombinant bacteria with plasmid pBR322 that has DNA inserted at BamHl lose tetracycline resistance.
Assertion (A) : Any fragment of DNA, when linked to the ori region, can be initiated to replicate.
Reason (R) : Ori is a genetic sequence that acts as the initiation site for replication of DNA.
The process of DNA replication begins at the ori sequence. The presence of ori in a DNA fragment makes it a self-replicating molecule.The process of DNA replication begins at the ori sequence. The presence of ori in a DNA fragment makes it a self-replicating molecule.
Assertion (A) : EcoRI is a restriction endonuclease enzyme.
Reason (R) : Exonuclease removes nucleotides from the ends of DNA.
EcoRI is a restriction endonuclease enzyme. Exonuclease removes nucleotides from the ends of DNA.
Assertion (A) : Restriction enzymes belong to class nucleases.
Reason (R) : Nucleases are of two kinds : exo and endonucleases. Exonucleases remove nucleotides within the DNA.
Nucleases are of two kinds : exo and endonucleases, but exonucleases remove nucleotides from the ends of the DNA.
Assertion (A) : It is essential to have few cloning sites in the cloning vector.
Reason(R) : It helps in identifying and eliminating non-transformants and selectively permitting the growth of the transformants.
It is essential to have few cloning sites in the cloning vector. It is because, in order to link the alien DNA, the vector needs to have very few recognition sites for the commonly used restriction enzymes. Presence of more than one recognition sites within the vector will generate several fragments, which will complicate the gene cloning. Also, the vector requires a selectable marker, which helps in identifying and eliminating non-transformants and selectively permitting the growth of the transformants.
Assertion (A) : Agarose gel electrophoresis is used to check the progression of a restriction enzyme digestion.
Reason (R) : Restriction enzyme digestions are performed by incubating purified DNA molecules with restriction enzymes.
In Agarose gel electrophoresis, DNAs fragments cut by restriction enzymes can be arranged according to their sizes.
Assertion (A) : A primer is a small segment of DNA that binds to a complementary strand of DNA.
Reason(R) : Primers are necessary to stop the functioning of DNA polymerase enzymes and, therefore, are necessary in polymerase chain reaction.
A primer is a small segment of DNA that binds to a complementary strand of DNA. Primers are necessary to start the functioning of DNA polymerase enzymes and, therefore, are necessary in polymerase chain reactions.
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Wrong (-)
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