Biotechnology: Principles, Techniques, and Applications

Chapter 1: Biotechnology, an Expanding Research Domain

Classical vs. Modern Biotechnology
- Classical Biotechnology:
  - Focuses on traditional methods such as cross-breeding and food preparation (e.g., fermentation).
  - It is limited by the species barrier, meaning genetic exchange typically only happens between related species.
  - The process of cross-breeding requires multiple generations to achieve desired traits.
- Modern Biotechnology/Genetic Engineering:
  - Involves direct adaptation and manipulation of DNA.
  - Creation of GGO (Genetically Modified Organisms):
    - Transgenic: Organisms containing DNA from a different species.
    - Cisgenic: Organisms containing DNA from the same species or a closely related species that could otherwise breed naturally.
  - Features: There is no species barrier, and results are achieved much faster than classical methods.
Domains of Application
- Red Biotech: Healthcare and Bio-pharmaceuticals.
  - Example: Production of human insulin.
- Green Biotech: Agriculture and Nutrition.
  - Example: Development of insect-resistant tobacco.
  - Case Study: Golden Rice. Project timeline: Started in 1991, field trials began in 2004, and the project was considered complete by 2020.
- White Biotech: Industrial production and degradation of chemical substances.
  - Example: Creating bioplastics derived from bio-ethanol.
- Blue Biotech: Sustainable use of marine resources.
  - Example: Sustainable cultivation of algae for the production of biofuel.
Biotechnology and Ethics
- Ethical Considerations (Pros and Cons):
  - Potential benefits of genetic selection/editing include high IQ, perfect vision, elimination of genetic diseases, superior athletic skills, and lower risks for Alzheimer's disease or heart attacks (infarcts).
  - Social opposition exists; for example, activists destroyed a GGO trial field in Wetteren.
- Global Scale of GGO Cultivation:
  - Data tracks hectares of GGO crop cultivation across various regions:
    - High concentration: > 10\text{ million} hectares.
    - Moderate concentration: > 1\text{ million} hectares.
    - Low concentration: $\le 1\text{ million}$ hectares.
    - Some regions have no clear data available.

Chapter 2: Biotechnological Techniques

PCR (Polymerase Chain Reaction)
- Definition: A technique used to massively replicate a specific segment of DNA.
- Components Required:
  - Nucleotides (dNTPs).
  - Primers (both reverse and forward).
  - Taq DNA polymerase (a heat-stable enzyme).
- Quantitative PCR (qPCR):
  - Used for measuring DNA concentration.
  - Mechanism:
    - Uses a probe labeled with a Reporter (R) (fluorescent agent) and a Quencher (Q) (which absorbs the fluorescence from the reporter).
    - Annealing: The primer and probe bind to the DNA.
    - Extension and Breakdown: As DNA polymerase extends the new strand from the $5'$ to $3'$ direction, it encounters the probe.
    - The probe is broken down; the reporter is released from the quencher.
    - Fluorescence Release: Once the reporter is free, it emits fluorescence which can be measured.
- Applications of PCR:
  - Used in NIPT (Non-Invasive Prenatal Testing) to diagnose Down syndrome in a fetus, which serves as a central point in the ethical debate regarding biotechnology.
DNA Gel Electrophoresis
- Definition: A method used to separate and organize DNA fragments based on their length.
- Apparatus and Materials:
  - Agarose solution (to create the gel).
  - Gel casting tray (gietbakje).
  - Comb (kam) to create slots (wells).
  - Electrophoresis chamber.
  - Colored loading solution.
- Process:
  - Samples are loaded into the slots of the gel.
  - An electric field is applied; DNA fragments (which are negatively charged) migrate toward the positive pole.
  - Smaller fragments migrate faster/further than larger fragments.
  - After migration, the gel is stained to reveal a banding pattern.
- Applications: Used for paternity testing and criminal identification (suspect identification).
DNA Sequencing
- Purpose: To determine the exact order of nucleotides in a DNA strand.
- Chain Termination Method (Sanger Sequencing):
  - Uses modified nucleotides called ddNTPs ( $ddGTP$ , $ddATP$ , $ddCTP$ , $ddTTP$ ) which stop DNA synthesis at specific bases.
  - This results in fragments of varying lengths that can be read to determine the sequence.
- Automatic Sequencing:
  - Uses fluorescent labels for each nucleotide type.
  - An electropherogram displays peaks of fluorescence intensity corresponding to the DNA length and sequence.
- Next Generation Sequencing (NGS):
  - Crucial for modern cancer research.
  - Process:
    - Primer binds to a single-stranded DNA anchored to a surface.
    - DNA polymerase adds a complementary base with a specific fluorophore.
    - Unincorporated nucleotides are washed away, and the fluorescence signal is measured.
    - The fluorophore and the chemical blockade are removed (cleaved), allowing the next base to be determined.
DNA Manipulation: Natural Gene Transfer
- Bacterial Mechanisms:
  - Transformation: Direct uptake of circular DNA or plasmids from the environment.
  - Conjugation: A process where a plasmid is copied and passed from one bacterium to another.
- Viral Mechanisms (Bacteriophages):
  - Transduction: DNA transfer mediated by a virus (bacteriophage).
- Bacterial Defense:
  - Bacteria use restriction enzymes to protect themselves against viral DNA by cutting it at specific sequences.
  - Examples of Restriction Enzymes:
    - $EcoRI$ derived from $Escherichia\,coli$ (R-strain).
    - $TaqI$ derived from $Thermus\,aquaticus$ .
    - $HaeIII$ derived from $Haemophilus\,aegyptus$ .
    - $HpaI$ derived from $Haemophilus\,parainfluenzae$ .
    - $HindIII$ derived from $Haemophilus\,influenzae$ (d-strain).
  - Cut Types: These enzymes produce either sticky ends (overhangs) or blunt ends (straight cut).
DNA Manipulation: Artificial Gene Transfer
- Using Plasmids as Vectors:
  - A plasmid is isolated from a bacterium and opened using a restriction enzyme.
  - Donor DNA is extracted and cut with the same restriction enzyme.
  - The desired donor DNA and the open plasmid are mixed; H-bridges form between complementary sticky ends.
  - The result is a recombinant plasmid containing both bacterial and donor DNA, which is then inserted into a host organism (making it transgenic).
- Historical Milestone: Montagu and Schell (1985).
  - Demonstrated gene transfer from bacteria to plants using the Ti-plasmid from a soil bacterium ( $Rhizobium\,radiobacter$ ).
  - Example: Inserting the gene for Bt-toxine from $Bacillus\,thurigiensis$ into plant cells, making the entire plant toxic to insects.
DNA Manipulation: Cloning and Gene Editing
- Cloning Types:
  - Natural Cloning: Occurs in nature, e.g., strawberry plants (runners).
  - Molecular Cloning: Replicating DNA fragments, e.g., for insulin production.
  - Reproductive Cloning: Creating a whole organism, e.g., Dolly the sheep.
  - Therapeutic Cloning: Research aimed at medical treatments.
- Gene Editing (CRISPR-Cas):
  - Provides precise control to "cut out" bad genes and replace them via substitution (synthetic gene), insertion (adding genes), or deletion (removing genes).
- CRISPR-Cas as a Bacterial Defense mechanism:
  - CRISPR Registry: Structured with identical, repeating CRISPR genes and unique spacer DNA (viral DNA from previous infections).
  - Mechanism:
    - First Infection: A Cas-nuclease (molecular scissors) cuts a piece of viral DNA (spacer DNA) and integrates it into the CRISPR registry.
    - Second Infection: The registry is transcribed into CRISPR-RNA (which includes the specific spacer RNA).
    - The CRISPR-RNA binds to the Cas-nuclease.
    - This CRISPR-RNA-Cas complex recognizes the matching region in the viral genome and cuts it into pieces, neutralizing the virus.