Biotechnology Overview: rDNA, Cloning, PCR, and Antibodies

Introduction to Recombinant DNA, Cloning & PCR

Objectives
  • Understand key terms:
    • Gene
    • Cloning
    • Polymerase Chain Reaction (PCR)
  • Examine steps of cloning.
  • Describe roles of enzymes in cloning:
    • Restriction endonucleases
    • Ligases
  • Explore plasmids and their roles:
    • Autonomous replication
  • Discuss expression systems used in cloning.
  • Outline PCR process steps.
Principles of Genomes
  • Definition of Genome: Complete set of genes or genetic material in a cell.
  • Genomics: Study of all DNA, including genes, relevant for biological research.
  • Importance: Provides key information for biological processes and can be manipulated to alter functions.
Genes Defined
  • Basic unit of inheritance; specify traits passed from parents to offspring.
  • Human genome: Approx. 20,000 protein-coding genes, <1.5% of DNA is coding (exons).
    • Introns: Non-coding regions of DNA.
    • Exons: Coding segments.
Gene Expression Process
  1. Transcription: DNA -> pre-mRNA -> mRNA (RNA splicing removes introns).
  2. Translation: mRNA -> Protein (requires ribosomes and tRNA for amino acids).
Cloning Process Overview
  • DNA Cloning: Amplification of specific DNA segments for study.
  • Steps in DNA Cloning:
    1. Obtain DNA segment.
    2. Select cloning vector (small DNA molecule).
    3. Covalently join DNA fragments.
    4. Introduce recombinant DNA into host.
    5. Identify host cells with recombinant DNA.
Cloning Vectors
  • Cloning vectors (e.g., plasmids) can replicate autonomously and include:
    • Bacterial artificial chromosomes (BACs)
    • Yeast artificial chromosomes (YACs)
  • Example - pBR322: Common synthetic plasmid with features for cloning.
Restriction Endonucleases
  • Function: Recognize and cleave DNA at specific sequences, resulting in sticky or blunt ends.
  • Types:
    • Type I and III: Complex, ATP-dependent enzymes.
    • Type II: Simpler, hydrolytic cleavage and palindromic recognition sequences (e.g., BamHI, HindIII).
DNA Ligases
  • Connect two DNA fragments, facilitating the final step of DNA cloning.
Expressing Cloned Genes
  • Expression Vectors: Contain transcription and translation signals for gene regulation (e.g., E. coli systems).
  • Benefits include high yield and specific activity of proteins produced.
Introduction to PCR
  • Definition: Amplification of a DNA segment to millions of copies within hours.
  • Uses:
    • Sequencing DNA
    • Forensic analysis
    • Genetic engineering
PCR Process Steps
  1. Denaturation: Heat causes DNA separation.
  2. Annealing: Cool to allow primers to attach to the target sequence.
  3. Extension: Taq polymerase synthesizes new DNA strands.
Reverse Transcriptase PCR (RT-PCR) and qPCR
  • Converts RNA into complementary DNA (cDNA) before amplification.
  • qPCR: Quantitative method, uses fluorescent dyes to track DNA concentration.
Introduction to Monoclonal Antibodies
Objectives
  • Understand antibody structures and functions.
  • Differentiate between monoclonal and polyclonal antibodies, including their varying forms (murine, chimeric).
Antibody Structure
  • IgG: Most common, consists of heavy and light chains with distinct antigen binding (Fab) and biological activity (Fc) portions.
  • Classes of antibodies:
    • IgG, IgM, IgA, IgD, IgE with various roles in immune response.
Monoclonal vs. Polyclonal Antibodies
  • Monoclonal Antibodies: Homogeneous, produced from a single clone (specific epitope binding).
  • Polyclonal Antibodies: Heterogeneous mix, multiple clones (varied epitope binding).
Applications of Monoclonal Antibodies
  • Treatment for:
    • Cancer
    • Autoimmune disorders
    • COVID-19
    • Other diseases in need of targeted therapy.
Production and Nomenclature of mAbs
Production Methods:
  • Hybridoma technology for producing stable mAbs.
  • Transgenic mice with humanized antibodies.
Protein Drugs
  • Significance: Key category of pharmaceuticals due to their role in various biological actions and minimal side effects compared to small molecules.
Protein Stability Challenges
  • Instability due to aggregation, chemical modifications, and denaturation.
  • Lyophilization: A method to enhance protein drug stability through freeze-drying processes.
Lyophilization Stages:
  1. Freezing: Solidify the product, preventing interactions.
  2. Primary Drying: Remove ice via sublimation.
  3. Secondary Drying: Desorb moisture remaining in matrix to enhance shelf-life.