Chapter 9: Biotechnology : Principles and Processes Assertion-Reason Questions | biology Class 12 CBSE

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 1

Logic Check

Assertion (A): Restriction endonucleases are also called 'molecular scissors'. Reason (R): They cut DNA at specific palindromic recognition sequences, generating fragments that can be used in recombinant DNA technology.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 2

Logic Check

Assertion (A): DNA is loaded at the cathode end in gel electrophoresis. Reason (R): DNA is a positively charged molecule and moves toward the cathode under an electric field.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 3

Logic Check

Assertion (A): The origin of replication (ori) is essential in a cloning vector. Reason (R): The ori sequence controls the replication of any linked alien DNA within the host cell and is also responsible for determining copy number.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 4

Logic Check

Assertion (A): In gel electrophoresis, larger DNA fragments migrate farther from the loading well than smaller fragments. Reason (R): Larger DNA fragments experience greater resistance while passing through the agarose gel matrix.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 5

Logic Check

Assertion (A): Bacterial cells are treated with calcium chloride solution before transformation with recombinant DNA. Reason (R): Calcium ions increase the efficiency of DNA entry into the bacterial cell by reducing the repulsion between the negatively charged DNA and the cell membrane.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 6

Logic Check

Assertion (A): Taq DNA polymerase is used in PCR. Reason (R): Taq polymerase is thermostable and remains active at the high temperatures required for denaturation of double-stranded DNA in each PCR cycle.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 7

Logic Check

Assertion (A): In blue-white selection, bacteria with recombinant plasmids form blue colonies on X-gal medium. Reason (R): Insertion of foreign DNA within the lacZ gene causes insertional inactivation, resulting in non-functional β-galactosidase and absence of blue pigment.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 8

Logic Check

Assertion (A): Ethidium bromide is used to stain DNA in gel electrophoresis. Reason (R): Ethidium bromide intercalates into DNA base pairs and fluoresces under UV light, making DNA bands visible.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 9

Logic Check

Assertion (A): In PCR, the same set of primers is used throughout all cycles. Reason (R): The primers are short, chemically synthesised oligonucleotides complementary to the two flanking regions of the target DNA, and they remain relevant in every denaturation-annealing-extension cycle.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 10

Logic Check

Assertion (A): A plasmid can serve as a vector to deliver foreign DNA into a host organism. Reason (R): Plasmids are large linear DNA molecules that replicate only with the host chromosome.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 11

Logic Check

Assertion (A): The Ti plasmid of Agrobacterium tumefaciens is used as a vector to introduce genes into plant cells. Reason (R): The Ti plasmid has the natural ability to transfer a segment of DNA (T-DNA) into the plant nuclear genome.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 12

Logic Check

Assertion (A): Both source DNA and vector DNA must be cut with the same restriction enzyme to create a functional recombinant DNA. Reason (R): The same restriction enzyme generates compatible sticky ends on both DNA molecules, which are required for their ligation by DNA ligase.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 13

Logic Check

Assertion (A): The downstream processing requirements are identical for all recombinant protein products. Reason (R): The nature and purity requirements of the desired product and the characteristics of the host cell vary from product to product.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 14

Logic Check

Assertion (A): Chitinase is used to break open fungal cells during DNA isolation. Reason (R): Fungal cell walls are composed mainly of chitin, which is degraded by chitinase to release cellular contents.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 15

Logic Check

Assertion (A): Recombinant DNA technology overcomes the limitations of traditional hybridisation in plant breeding. Reason (R): Traditional hybridisation introduces only desired genes without any undesirable genes from the donor organism.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 16

Logic Check

Assertion (A): In pBR322, insertion of foreign DNA at the BamHI site results in loss of tetracycline resistance. Reason (R): The BamHI site is located within the tetR gene; inserting foreign DNA disrupts this gene by insertional inactivation.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 17

Logic Check

Assertion (A): Bacteriophages are preferred over plasmids when a very high number of copies of the cloned DNA is required. Reason (R): Bacteriophages have a higher copy number per cell than most plasmids, producing more copies of the cloned insert.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 18

Logic Check

Assertion (A): The biolistics (gene gun) method is suitable for introducing foreign DNA into plant cells. Reason (R): High-velocity microparticles of gold or tungsten coated with DNA physically penetrate the plant cell wall and membrane to deliver the DNA.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 19

Logic Check

Assertion (A): In modern biotechnology, genetically modified organisms are used to achieve large-scale production of useful products. Reason (R): Traditional biotechnology like bread and wine making also employs genetically modified organisms.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 20

Logic Check

Assertion (A): HindII was the first restriction endonuclease to be isolated and characterised. Reason (R): HindII recognised a specific sequence of six base pairs and always cut DNA at that particular point.

Reasoning Options

ByteNotes

Chapter sections

Chapter 9: Biotechnology : Principles and Processes | Assertion-Reason

Assertion (A): Restriction endonucleases are also called 'molecular scissors'. Reason (R): They cut DNA at specific palindromic recognition sequences, generating fragments that can be used in recombinant DNA technology.

Assertion (A): DNA is loaded at the cathode end in gel electrophoresis. Reason (R): DNA is a positively charged molecule and moves toward the cathode under an electric field.

Assertion (A): The origin of replication (ori) is essential in a cloning vector. Reason (R): The ori sequence controls the replication of any linked alien DNA within the host cell and is also responsible for determining copy number.

Assertion (A): In gel electrophoresis, larger DNA fragments migrate farther from the loading well than smaller fragments. Reason (R): Larger DNA fragments experience greater resistance while passing through the agarose gel matrix.

Assertion (A): Bacterial cells are treated with calcium chloride solution before transformation with recombinant DNA. Reason (R): Calcium ions increase the efficiency of DNA entry into the bacterial cell by reducing the repulsion between the negatively charged DNA and the cell membrane.

Assertion (A): Taq DNA polymerase is used in PCR. Reason (R): Taq polymerase is thermostable and remains active at the high temperatures required for denaturation of double-stranded DNA in each PCR cycle.

Assertion (A): In blue-white selection, bacteria with recombinant plasmids form blue colonies on X-gal medium. Reason (R): Insertion of foreign DNA within the lacZ gene causes insertional inactivation, resulting in non-functional β-galactosidase and absence of blue pigment.

Assertion (A): Ethidium bromide is used to stain DNA in gel electrophoresis. Reason (R): Ethidium bromide intercalates into DNA base pairs and fluoresces under UV light, making DNA bands visible.

Assertion (A): In PCR, the same set of primers is used throughout all cycles. Reason (R): The primers are short, chemically synthesised oligonucleotides complementary to the two flanking regions of the target DNA, and they remain relevant in every denaturation-annealing-extension cycle.

Assertion (A): A plasmid can serve as a vector to deliver foreign DNA into a host organism. Reason (R): Plasmids are large linear DNA molecules that replicate only with the host chromosome.

Assertion (A): The Ti plasmid of Agrobacterium tumefaciens is used as a vector to introduce genes into plant cells. Reason (R): The Ti plasmid has the natural ability to transfer a segment of DNA (T-DNA) into the plant nuclear genome.

Assertion (A): Both source DNA and vector DNA must be cut with the same restriction enzyme to create a functional recombinant DNA. Reason (R): The same restriction enzyme generates compatible sticky ends on both DNA molecules, which are required for their ligation by DNA ligase.

Assertion (A): The downstream processing requirements are identical for all recombinant protein products. Reason (R): The nature and purity requirements of the desired product and the characteristics of the host cell vary from product to product.

Assertion (A): Chitinase is used to break open fungal cells during DNA isolation. Reason (R): Fungal cell walls are composed mainly of chitin, which is degraded by chitinase to release cellular contents.

Assertion (A): Recombinant DNA technology overcomes the limitations of traditional hybridisation in plant breeding. Reason (R): Traditional hybridisation introduces only desired genes without any undesirable genes from the donor organism.

Assertion (A): In pBR322, insertion of foreign DNA at the BamHI site results in loss of tetracycline resistance. Reason (R): The BamHI site is located within the tetR gene; inserting foreign DNA disrupts this gene by insertional inactivation.

Assertion (A): Bacteriophages are preferred over plasmids when a very high number of copies of the cloned DNA is required. Reason (R): Bacteriophages have a higher copy number per cell than most plasmids, producing more copies of the cloned insert.

Assertion (A): The biolistics (gene gun) method is suitable for introducing foreign DNA into plant cells. Reason (R): High-velocity microparticles of gold or tungsten coated with DNA physically penetrate the plant cell wall and membrane to deliver the DNA.

Assertion (A): In modern biotechnology, genetically modified organisms are used to achieve large-scale production of useful products. Reason (R): Traditional biotechnology like bread and wine making also employs genetically modified organisms.

Assertion (A): HindII was the first restriction endonuclease to be isolated and characterised. Reason (R): HindII recognised a specific sequence of six base pairs and always cut DNA at that particular point.

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