Chapter 4.1 and 4.2

Introduction to Studying DNA

  • Learning Outcomes:

    • Describe the structure and function of DNA.

    • Explain the process by which DNA encodes proteins.

    • Understand molecular modeling in studying DNA and biomolecules.

    • Differentiate eukaryotic vs. prokaryotic chromosomal structures & gene regulation.

    • Compare bacterial cultures in liquid vs. solid media; learn sterile techniques for media preparation.

    • Discuss virus characteristics and their role in genetic engineering.

    • Explain genetic engineering processes with applications such as recombinant DNA technology, site-specific mutagenesis, and gene therapy.

    • Describe gel electrophoresis and its relation to molecular characteristics and migration.

DNA Structure and Function

  • DNA and Biotechnology:

    • Innovations in DNA transfer/manipulation have created the modern biotechnology sector.

    • Techniques for isolating and studying DNA have led to new biotechnological applications.

  • Biological Role of DNA:

    • DNA consists of genetic information, transcribed into RNA, which then translates into amino acids/proteins.

    • Involvement in protein synthesis dictates cell functions and organism traits.

  • Central Dogma of Biology:

    • Flow of genetic information: DNA ➜ RNA ➜ Protein.

Genetic Complexity and Organization

  • Human Genes:

    • Humans possess approximately 20,000-25,000 genes that code for various proteins.

    • A typical cell has 2000+ protein types, with possible billions in multicellular organisms.

    • The genome varies by organism but remains consistent within the organism’s cells (excluding sex cells).

DNA Characteristics

  • Key Components of DNA:

    • Gene: Segment of DNA that codes for a specific protein.

    • Nitrogenous Bases:

      • Adenine (A), Thymine (T), Cytosine (C), Guanine (G).

    • Structure:

      • DNA forms a double helix; nucleotides are linked by phosphodiester bonds and held together by hydrogen bonds.

      • Base pairing: A-T, G-C, with antiparallel strand orientation.

Variations in DNA Structure

  • Differences across Organisms:

    • Variation exists in:

      • Number of chromosomes (Prokaryotes vs. Eukaryotes).

      • Length and coding of DNA.

      • Shape (circular vs. linear chromosomes).

Prokaryotic DNA

  • Characteristics of Prokaryotes:

    • Bacteria like E. coli have circular DNA, typically one chromosome attached to the membrane, known as nucleoid.

    • Plasmids (extra loops of DNA) provide additional traits such as antibiotic resistance.

  • Gene Expression Control:

    • Operons regulate gene expression (comprises promoter, operator, structural genes).

Eukaryotic DNA

  • Eukaryotic DNA Structure:

    • Multiple linear chromosomes wrapped around histone proteins.

    • Larger genomic size compared to prokaryotes; typically 46 chromosomes in humans.

  • Gene Expression Mechanism:

    • Eukaryotic genes can be turned up or down using enhancers or silencers.

    • Introns (non-coding) are spliced out during mRNA processing to leave only exons (coding sequences).

Cell Culturing Techniques

  • Growing Bacteria:

    • Bacteria can be grown in liquid (broth) or solid (agar) media.

    • Media preparation must be sterile to prevent contamination.

    • Autoclaving is essential for sterilization.

Viral Impact on Biotechnology

  • Viruses in Genetic Engineering:

    • While not living, viruses like bacteriophages serve as vectors in genetic therapy and engineering.

    • Viruses infect cells and may integrate their nucleic acid with host DNA for replication.

Gene Therapy

  • Concept:

    • Rectify defective genes in individuals therefore treating genetic disorders.

    • Utilizes recombinant DNA technology to insert corrective genes into cells.