Biotechnology

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Biotechnology — Quick Facts

Key Definitions:

• Biotechnology: The use of living organisms, systems, or processes to develop products and technologies that improve human life
• Genetic Engineering: Direct manipulation of an organism’s genome using biotechnology
• Recombinant DNA: DNA molecules formed by combining genetic material from different sources
• Gene Cloning: Creating identical copies of a specific gene

Core Techniques:

• PCR (Polymerase Chain Reaction): Amplifies specific DNA sequences
• Gel Electrophoresis: Separates DNA fragments by size
• Restriction Enzymes: Cut DNA at specific sequences
• Vectors (Plasmids): Carry foreign DNA into host cells

⚡ Exam Tips for MDCAT:

• Restriction enzymes are named after the organism they were derived from — e.g., EcoRI from E. coli strain R
• The insulin production cycle using E. coli is a favourite MDCAT question
• Distinguish between upstream and downstream processing
• Remember the difference between gene therapy (somatic) and germline engineering

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🟡 Standard — Regular Study (2d–2mo)

For students who want genuine understanding.

Biotechnology — Study Guide

Gene Cloning Process:

1. Isolation of Gene of Interest: Using restriction enzymes to cut DNA at specific sites
2. Insertion into Vector: Ligating the gene into a plasmid (vector)
3. Transformation: Introducing recombinant plasmid into host cell (E. coli is most common)
4. Selection: Using antibiotic resistance markers to identify transformed cells
5. Expression: The host cell expresses the foreign gene and produces the protein

Key Tools in Biotechnology:

Tool	Function	Example Use
Restriction Enzymes	Cut DNA at specific sequences	HindIII cuts at AAGCTT
DNA Ligase	Joins DNA fragments	Creates recombinant DNA
Plasmids	Circular DNA vectors	Cloning vectors
PCR	Amplify DNA	DNA fingerprinting
Gel Electrophoresis	Separate DNA by size	DNA profiling

Applications of Biotechnology:

• Medicine: Production of insulin (Humulin), human growth hormone, vaccines (Hepatitis B), interferons
• Agriculture: Bt cotton (produces insecticide), herbicide-resistant crops, golden rice (vitamin A)
• Industry: Biodegradable plastics (PHB), enzymes in detergent, biofuelling
• Environmental: Bioremediation (oil-eating bacteria), biosensors

DNA Fingerprinting (Forensic Science):

• Uses Variable Number Tandem Repeats (VNTRs)
• Short tandem repeats (STRs) are analysed
• Gel electrophoresis separates fragments by size
• Pattern match identifies individuals (99.99% accuracy)

Common Student Mistakes:

• Confusing gene cloning with reproductive cloning
• Thinking all bacteria are harmful — E. coli K12 is a workhorse in biotechnology
• Mixing up restriction endonucleases (cut DNA) with ligases (join DNA)

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🔴 Extended — Deep Study (3mo+)

Comprehensive theory for thorough preparation.

Biotechnology — Comprehensive Notes

Recombinant DNA Technology — Step by Step:

Step 1: Cutting DNA

• Restriction endonucleases recognise specific palindromic sequences (4-8 base pairs)
• EcoRI recognises: 5’-GAATTC-3’
• Creates sticky ends (overhanging) or blunt ends
• BamHI: GGATCC | HindIII: AAGCTT | SalI: GATCG

Step 2: Joining DNA

• DNA ligase forms phosphodiester bonds
• T4 DNA ligase is most commonly used
• Requires ATP and Mg$^{2+}$

Step 3: Vector Design

• Plasmids: Small circular DNA, 2-10 kb
• Phage vectors: Lambda ($\lambda$) phage, up to 25 kb
• Cosmids: Hybrid plasmid-phage, up to 45 kb
• BACs (Bacterial Artificial Chromosomes): Up to 300 kb
• YACs (Yeast Artificial Chromosomes): Up to 1000 kb

Expression Vectors:

• Require promoter (e.g., lac promoter for inducible expression)
• Require terminator sequence
• May include tag sequences (His-tag for purification)

Human Insulin Production:

Prior to 1982, insulin was extracted from pig and cow pancreas (porcine/bovine insulin). In 1978, Genentech produced synthetic human insulin using E. coli:

1. Synthesise insulin gene (A and B chains)
2. Insert into plasmid vector with lac operator
3. Transform into E. coli
4. Add IPTG to induce transcription
5. Cells produce insulin chains
6. Purify and chemically join chains

Gene Therapy:

• Somatic Gene Therapy: Modifies body cells, changes not inherited
  • ADA deficiency (adenosine deaminase) — first approved gene therapy (1990)
  • CAR-T cell therapy for cancer
• Germline Gene Therapy: Modifies gametes/embryos, inherited (ethically controversial, illegal in most countries)

PCR (Polymerase Chain Reaction):

• Invented by Kary Mullis (1983)

• Components: Template DNA, primers, Taq polymerase (heat-stable), dNTPs

• Steps:

  1. Denaturation: 94-95°C — strands separate
  2. Annealing: 50-65°C — primers bind
  3. Extension: 72°C — Taq polymerase synthesises

• Number of cycles: After n cycles, copy count = $2^n$

• After 30 cycles: $\approx 10^9$ copies from a single molecule

CRISPR-Cas9 Gene Editing:

• CRISPR: Clustered Regularly Interspaced Short Palindromic Repeats
• Cas9: Endonuclease protein
• Guide RNA (gRNA) directs Cas9 to specific DNA sequence
• Creates double-strand break, cellular repair introduces mutation
• 2012: Jennifer Doudna and Emmanuelle Charpentier demonstrated use
• 2020: Nobel Prize in Chemistry

⚡ MDCAT High-Yield Patterns:

• The lac operon system is often used to explain controlled gene expression in biotechnology
• Questions on ethical concerns of genetic engineering are increasing
• Bt cotton and insulin production are commonly asked applications
• Remember that selectable markers (like antibiotic resistance) help identify transformed cells

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