NCERT Solutions for Class 12 Biology Chapter 9 Biotechnology Principles and Processes
NCERT Solutions for Class 12 Biology Chapter 9 Biotechnology: Principles and Processes covers Principles of Genetic Engineering, Tools of Recombinant DNA Technology, Restriction Enzymes, Cloning Vectors, Competent Host, PCR, Gel Electrophoresis, and Bioreactors.
Overview of Topics & Subtopics (Click to Jump)
1. Principles of Biotechnology & Recombinant DNA Technology
Short Note:
• Core Techniques of Biotechnology:
1. Genetic Engineering: Techniques to alter chemistry of genetic material (DNA/RNA) to introduce into host organisms and change their phenotype.
2. Bioprocess Engineering: Maintenance of sterile conditions in chemical engineering processes to grow target microorganism/cell in large quantities.
• First Recombinant DNA (rDNA): Constructed by Stanley Cohen and Herbert Boyer in 1972 by linking an antibiotic resistance gene with a native plasmid of Salmonella typhimurium.
2. Tools of Recombinant DNA Technology
Short Note:
• Restriction Enzymes ('Molecular Scissors'): Cut DNA at specific palindromic nucleotide sequences.
- Exonucleases: Remove nucleotides from the ends of DNA.
- Endonucleases: Cut at specific positions within the DNA (e.g., EcoRI recognizes 5'-GAATTC-3').
• Cloning Vectors: Vehicles used to transfer foreign DNA into host cells. E.g., Plasmids (pBR322) and Bacteriophages.
- Key Features: Origin of Replication (ori), Selectable Marker (ampR, tetR), and Cloning Sites.
• Competent Host: Host made capable of taking up foreign DNA (e.g., treating bacterial cells with divalent cation Calcium Ca2+ followed by heat shock treatment at 42°C).
3. Processes of Recombinant DNA Technology & Bioreactors
Short Note:
• Gel Electrophoresis: Method to separate DNA fragments according to their size under an electric field through agarose gel matrix. DNA fragments are negatively charged and move towards the anode. Visualized using Ethidium Bromide (EtBr) under UV light (bright orange bands).
• Polymerase Chain Reaction (PCR): In vitro amplification of gene of interest in 3 steps: Denaturation (94°C), Annealing (54°C), and Extension (72°C) using thermostable Taq DNA polymerase (isolated from Thermus aquaticus).
• Bioreactors: Large vessels (100–1000 L) providing optimal conditions (pH, temperature, oxygen, nutrients) for processing raw materials biologically into specific products. E.g., Simple stirred-tank bioreactor.
Intext & Conceptual Questions
| Feature | Exonucleases | Endonucleases |
|---|---|---|
| Site of Action | Cleave/remove nucleotides from the outer terminal ends of DNA. | Cut at specific internal sites within the DNA strand. |
| Palindromic Requirement | Do not require specific palindromic sequences. | Require specific palindromic recognition sequences. |
| Sticky Ends | Do not produce sticky ends. | Produce sticky or blunt ends. |
| Example | Exonuclease III | EcoRI, HindIII, BamHI |
1. Denaturation: High temperature (~94°C) breaks hydrogen bonds between double-stranded target DNA, separating it into single strands.
2. Annealing: Temperature is lowered (~50-60°C) to allow two oligonucleotide primers to hybridize to complementary regions on single-stranded DNA.
3. Extension: Thermostable Taq DNA polymerase extends the primers by adding dNTPs at ~72°C, synthesizing complementary strands.
Textbook Chapter End Exercise Questions
Restriction Endonucleases: Enzmyes that inspect double-stranded DNA and cut both strands at specific palindromic nucleotide recognition sequences.
Naming Convention (e.g., EcoRI):
• E: Represents the genus Escherichia.
• co: Represents the species coli.
• R: Represents the strain RY13.
• I: Roman numerical indicating the order in which the enzyme was isolated from that strain of bacteria.
1. Origin of Replication (ori): Specific sequence from where replication starts; controls copy number of linked foreign DNA.
2. Selectable Marker: Genes helping to identify and eliminate non-transformants while permitting selective growth of transformants (e.g., ampR, tetR genes).
3. Cloning / Recognition Sites: Presence of unique restriction sites for restriction enzymes to link foreign DNA.
4. Small Size: Low molecular weight makes isolation and manipulation easier.
Bioreactor: A large vessel (100-1000 L) in which biological raw materials are converted into specific recombinant products, enzymes, or biomass under optimal environmental conditions.
Components of Stirred-Tank Bioreactor:
• Agitator System: Ensures continuous mixing and even distribution of oxygen and nutrients.
• Oxygen Delivery System: Sparger to bubble sterile air.
• Foam Control System: Prevents foam accumulation.
• Temperature & pH Control System: Maintains ideal growth conditions.
• Sampling Port: Allows periodic withdrawal of small cultures for testing.
Read More & Chapter Resources
These short notes are designed for quick revision. Read the main points once, then use the related material below to practise the same chapter. Revising a concept and checking it with questions can make your preparation more focused.