Unit 5
Biotechnology
Chapter 5.1
BiotechnologyClass 12 Biology – Biotechnology Notes PDF
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Introduction
Modern biotechnology includes recombinant DNA technology, cloning vectors, restriction enzymes, PCR, gene transfer and applications in medicine, agriculture, industry and research.
1. Basic Tools of Genetic Engineering
Restriction Enzymes
Cut DNA at specific recognition sequences and generate DNA fragments.
DNA Ligase
Joins DNA fragments by forming phosphodiester bonds.
Vectors
DNA molecules such as plasmids used to carry foreign DNA into a host cell.
Host Cells
Cells that receive recombinant DNA and support replication or expression.
Fig. 1 – Restriction Enzyme and DNA Ligase
2. Recombinant DNA Technology
Main Steps
- Identify and isolate the gene or DNA fragment of interest.
- Cut donor DNA and vector with suitable restriction enzyme(s).
- Join the desired fragment to the vector using DNA ligase.
- Introduce recombinant vector into a host cell.
- Select host cells that contain the recombinant DNA.
- Multiply the cells and, when required, express the inserted gene.
Fig. 2 – Recombinant DNA Workflow
3. Plasmid as a Cloning Vector
A plasmid is a small circular DNA molecule commonly found in bacteria. An engineered plasmid vector typically contains an origin of replication, selectable marker and one or more cloning sites.
Fig. 3 – Simplified Plasmid Vector
4. Polymerase Chain Reaction (PCR)
Three Main Steps
- Denaturation: double-stranded DNA separates.
- Annealing: primers bind to complementary target sequences.
- Extension: a thermostable DNA polymerase synthesizes new strands.
Fig. 4 – PCR Cycle
5. Gel Electrophoresis
Gel electrophoresis separates DNA fragments mainly according to size. DNA is negatively charged and migrates through a gel toward the positive electrode when an electric field is applied.
Fig. 5 – DNA Gel Electrophoresis
6. Applications of Biotechnology
Medicine
Production of recombinant proteins, molecular diagnosis and development of biological products.
Agriculture
Crop improvement, tissue culture, disease resistance and genetic analysis.
Industry
Use of microbes and enzymes in food, fermentation and industrial bioprocesses.
Research
Gene cloning, DNA amplification, sequencing and functional studies.
Fig. 6 – Main Areas of Biotechnology
7. Quick Revision & Exam Points
- Define biotechnology.
- What are restriction enzymes and DNA ligase?
- Explain recombinant DNA technology.
- Draw a plasmid vector.
- Define PCR and explain its three steps.
- What is gel electrophoresis?
- List major applications of biotechnology.
- Restriction enzyme → cuts DNA.
- Ligase → joins DNA.
- Vector → carries foreign DNA.
- Plasmid = common cloning vector.
- PCR amplifies DNA.
- PCR cycle = denaturation → annealing → extension.
- Gel electrophoresis separates DNA fragments.
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