Class 12 Biology Chapter 11 – Biotechnology: Principles and Processes

 ✍️ Chapter 11: Biotechnology: Principles and Processes

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🔶 Introduction to Biotechnology

Biotechnology is the branch of biology that deals with the use of living organisms and biological systems to develop products and technologies for human use.

Modern biotechnology involves genetic engineering and bioprocess engineering.

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🔷 Principles of Biotechnology

There are two core techniques that enabled the growth of modern biotechnology:

1. Genetic Engineering – Altering the chemistry of genetic material (DNA/RNA) to introduce desirable traits.

2. Bioprocess Engineering – Maintenance of sterile conditions to allow growth of only the desired microbe.

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🧬 Tools of Recombinant DNA Technology

1. Restriction Enzymes (Molecular Scissors)

Cut DNA at specific sites called recognition sequences.

Example: EcoRI – Cuts between G and A in GAATTC.

Types:

Exonucleases – Remove nucleotides from ends.

Endonucleases – Cut within the DNA.

📌 Diagram: Action of Restriction Endonuclease on DNA

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2. Cloning Vectors

DNA molecules that can carry a foreign DNA segment.

Example: Plasmid (circular DNA found in bacteria).

Features of ideal vector:

Origin of replication (ori)

Selectable marker (antibiotic resistance gene)

Cloning site (recognition sites)

📌 Diagram: Structure of Plasmid

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3. Competent Host (Cells)

Cells made capable of accepting foreign DNA.

Made competent using methods like CaCl₂ treatment and heat shock.

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🔶 Steps in Recombinant DNA Technology

1. Isolation of DNA

Cell is lysed using enzymes to extract DNA.

2. Cutting of DNA at Specific Sites

Using restriction enzymes, both vector and gene of interest are cut.

3. Amplification of Gene using PCR

Polymerase Chain Reaction (PCR) is used to amplify (multiply) DNA segments.

Enzyme used: Taq polymerase

📌 Diagram: PCR Process (Denaturation → Annealing → Extension)

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4. Insertion of Recombinant DNA into Host

Ligation of gene into plasmid using DNA ligase.

Recombinant plasmid introduced into host cell (E. coli).

5. Selection of Recombinants

Use of antibiotic resistance genes to select recombinant cells.

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🔷 Bioreactors

Large vessels in which raw materials are biologically converted into specific products.

Maintains temperature, oxygen, pH, and nutrients.

📌 Diagram: Structure of Bioreactor (Stirred Tank Bioreactor)

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🔶 Downstream Processing

Involves separation, purification, and packaging of the product.

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✅ Summary Points

Genetic engineering involves cutting and pasting DNA.

Restriction enzymes recognize palindromic sequences.

Vectors are vehicles to carry genes.

PCR helps in DNA amplification.

Bioreactors produce large-scale products.

Recombinant DNA technology has wide applications in medicine, agriculture, and research.

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🧠 Important Terms to Remember

Term Description

Plasmid Circular DNA used as vector

Restriction Enzyme Enzyme that cuts DNA at specific sites

PCR Polymerase Chain Reaction, used to amplify DNA

Ligase Enzyme that joins DNA fragments

Competent Cell Cell that can accept foreign DNA

Bioreactor Vessel for large-scale biological product production

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📌 Important Diagrams:

1. Action of Restriction Endonuclease on DNA

2. Structure of Plasmid

3. PCR Cycle

4. Bioreactor (Stirred-tank type)

PCR cycle and structure of plasmid is very important diagrams.

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✅ Written by: Shahid – Study with Shahid

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