Biotechnology: Principles and Processes — Class 12 MCQs with Answers

Biotechnology: Principles and Processes — important questions & MCQs with answers (Class 12 Biology)

6 solved questions from this chapter's difficulty levels, each with its answer and explanation. Tap an option to check yourself.

0 of 6 answered

1. Q1 of 6Easy

   Restriction enzymes:

   ATranslate proteinsBJoin DNA fragmentsCReplicate DNADCut DNA at specific sequences
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   Answer: Cut DNA at specific sequences

   Explanation: Restriction endonucleases recognise short palindromic sequences (e.g. GAATTC for EcoRI) and cut both strands there, acting as molecular scissors — ligase joins fragments, it doesn't cut them.

2. Q2 of 6Easy

   PCR (Polymerase Chain Reaction) is used to:

   AAmplify (make many copies of) a DNA segmentBCut DNACTranslate mRNADJoin DNA
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   Answer: Amplify (make many copies of) a DNA segment

   Explanation: PCR (polymerase chain reaction) amplifies a target DNA segment exponentially in a test tube using primers and Taq polymerase — it copies DNA, it does not cut or join it.

3. Q3 of 6Medium

   Common cloning vector:

   ARibosomeBPlasmidCMitochondrionDVacuole
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   Answer: Plasmid

   Explanation: Plasmids are small, circular, self-replicating extra-chromosomal DNA in bacteria; their independent origin of replication lets them carry and multiply a foreign gene inside the host.

4. Q4 of 6Medium

   PCR thermocycler key enzyme:

   ALipaseBDNaseCTaq DNA polymeraseDAmylase
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   Answer: Taq DNA polymerase

   Explanation: Taq polymerase, from the thermophile Thermus aquaticus, survives the ~94-95°C denaturation step of every PCR cycle without unfolding, unlike ordinary heat-sensitive DNA polymerases.

5. Q5 of 6Hard

   Assertion: The same restriction enzyme is used to cut both vector and insert. Reason: It generates identical complementary sticky ends that ligate easily. Choose the correct option.

   ABoth true and reason explains assertionBBoth true, reason does not explainCAssertion true, reason falseDBoth false
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   Answer: Both true and reason explains assertion

   Explanation: Using the same restriction enzyme on both vector and insert really does generate matching complementary sticky ends, which anneal and ligate efficiently — the reason correctly explains the assertion.

6. Q6 of 6Hard

   Bioreactors:

   ACooking potsBLarge vessels for industrial culture of cellsCChemical batteriesDBurners
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   Answer: Large vessels for industrial culture of cells

   Explanation: Bioreactors are large vessels that maintain optimum temperature, pH, substrate and oxygen for growing cells or enzymes at industrial scale to synthesise a desired biotech product.

Biotechnology: Principles and Processes notes: key concepts (Class 12 Biology)

Biotechnology tools and processes: restriction enzymes, cloning vectors (plasmids, Ti plasmid), ligase and competent host cells; the steps of recombinant DNA technology; gel electrophoresis to separate DNA; PCR to amplify it; methods of introducing DNA into cells; and bioreactors with downstream processing.

Restriction enzymes

Molecular scissors — restriction endonucleases cut DNA at specific palindromic recognition sites; e.g., EcoRI cuts G^AATTC leaving sticky (cohesive) ends.

Sticky ends

Single-stranded overhangs left by a staggered cut; complementary overhangs from the same enzyme let vector and insert join easily via ligase.

DNA ligase

Molecular glue that joins DNA fragments by sealing the phosphodiester backbone; used to seal foreign DNA into a vector.

Cloning vector

A DNA carrier (usually a plasmid) with an origin of replication (ori), selectable markers and recognition sites; carries foreign DNA into a host.

Ti plasmid

Tumour-inducing plasmid of Agrobacterium tumefaciens; disarmed and used as a natural vector to make transgenic plants (transfers its T-DNA).

Selectable markers

Genes (e.g., antibiotic resistance) that identify transformed cells; insertional inactivation and blue-white (β-galactosidase) screening detect recombinants.

Competent host cell

A cell made able to take up DNA — by CaCl₂ treatment then a brief 42°C heat shock; E. coli is the commonest host in genetic engineering.

Gel electrophoresis

Separates DNA fragments by size in an agarose gel; negatively charged DNA moves to the anode, smaller fragments travelling farther. Stained by ethidium bromide.

PCR

Polymerase Chain Reaction amplifies a DNA segment in vitro through cycles of denaturation (~94°C), primer annealing and extension by heat-stable Taq polymerase.

Primers

Short single-stranded DNA sequences that flank the target and provide a starting point for synthesis in PCR; they determine the reaction's specificity.

Bioreactor

A vessel (e.g., stirred-tank) for large-scale culture; controls temperature, pH, oxygen, substrate and agitation to maximise product yield.

Downstream processing

Post-production separation and purification of the product, then formulation with preservatives and quality control before it is marketed.

Gene gun & microinjection

Ways to introduce DNA — biolistics (gene gun) shoots DNA-coated metal particles into cells; microinjection injects DNA directly into a cell nucleus.

Transformation

Uptake of foreign DNA by a host cell; the recombinant DNA then replicates and is expressed inside the host to give the desired product.