Molecular Biology and Diagnostics

INTRODUCTION TO MOLECULAR BIOLOGY AND DIAGNOSTICS

GOAL OF CELL AND MOLECULAR BIOLOGY

  • To understand and explain the molecular basis of a cell and its function.
  • Focus on cellular processes including:
  • Cellular reproduction
  • Gene expression
  • Signal transduction
  • Cell motility
  • Tissue formation during development and wound healing.
  • Utilizes multidisciplinary experimental approaches:
  • Biochemical and biophysical methods
  • Molecular and genetic manipulation of cellular functions.

METHODOLOGICAL APPROACH

  • Uses Reductionist Philosophy:
  • Focus on breaking down complex biological processes into simpler components.
  • 20th-century human perceptions of life include:
    1. Vitalism: Study intact cells.
    2. Holism: The whole is greater than the sum.
    3. Mechanism: Analyze cells like machines.
    4. Reductionism: Biological explanations based on physics and chemistry.

MAJOR THEORIES OF BIOLOGY

Evolution Theory - Darwin’s Natural Selection

  • Proposed by Charles Darwin.
  • Describes changes in allele frequency across generations influenced by habitat.
  • Natural selection leads to better adaptation and progressive evolutionary change.

Cell Theory

  • Key principles:
  1. All organisms consist of one or more cells.
  2. Life functions occur within cells.
  3. All cells originate from pre-existing cells.
  • LUCA: Common ancestor from which all life evolved 3-4 billion years ago.
  • Types of cell division:
  1. Mitosis: Somatic cells and unicellular eukaryoic asexual reproduction.
  2. Meiosis: Production of gametes in sexual reproduction.

SCIENTISTS THAT CONTRIBUTED TO BIOLOGY

  • Matthias Schleiden: All plants are made of cells.
  • Theodore Schwann: All animals consist of cells.
  • Rudolf Virchow: Cells arise from pre-existing cells.

EARLY HISTORICAL MILESTONES

  • Molecular biology integrates genetics, biochemistry, cell biology, etc.
  • William Astbury, 1945: Defined molecular biology's study scope on biomolecular structures.

BIOMOLECULES AND CELLS

  • Cells: Fundamental unit of life, varying in shapes, sizes, and functions.
  • Common basic chemistry across living cells:
  • Genetic information flows: DNA → RNA → Protein (Gene expression).

MOLECULAR STRUCTURES IN CELLS

Organic Molecules

  • Contain carbon skeleton, typically large, and bonded via covalent bonds.

Inorganic Molecules

  • Usually lack carbon; often consist of various elements and ionic bonds (e.g., salts).

Functional Groups

  • Key functional groups in biomolecules:
  • Hydroxyl (OH)
  • Amino (NH₂)
  • Phosphate (H₂PO₄)

MONOMERS AND POLYMERS

  • Polymers formed from monomers through dehydration reactions.
  • Breakdown through hydrolysis reactions.

Major Classes of Organic Compounds

  1. Carbohydrates
  • Functions: Energy production/storage, structural support.
  • Types: Monosaccharides, disaccharides, oligosaccharides, polysaccharides (e.g., starch, glycogen, cellulose).
  1. Lipids
  • Fatty acids: Hydrophobic hydrocarbon chains with carboxyl groups. Types include saturated (solid) and unsaturated (liquid).
  • Functions: Energy storage, membrane formation.
  1. Proteins
  • Composed of amino acids; structure defined by peptide bonds.
  • Functions: Enzymatic activity, defense, transport, support, motility, regulation, storage.
  • Grouped into essential (must be consumed) and nonessential (produced by the body).
  1. Nucleic Acids
  • Comprised of nucleotides forming DNA and RNA.
  • Codes for proteins; includes a sugar, phosphate, and nitrogenous base.
  • DNA contains deoxyribose; RNA contains ribose.

THE GENETIC CODE

  • Composed of DNA instructions to synthesize proteins, using codons made of nucleotide bases (A, T, C, G).

NUCLEIC ACIDS AND MACROMOLECULES

  • Nucleotide structure: phosphate group, sugar, nitrogenous base.
  • Phosphodiester bonds link nucleotides to form nucleic acids, giving DNA directionality (5’ to 3’).

DNA & Chromosome Structure

  • Features an antiparallel double-helix structure.
  • Chromatin includes nucleosomes (DNA + histones).
  • Chromosome visibility during cell division, with distinct telomeres and centromeres.

Historical Advances in Molecular Biology

  • Significant research milestones include sequencing genomes from various organisms, ultimately leading to the Human Genome Project (2001).

APPROACHES IN RESEARCH

  • In vitro (lab settings), in vivo (living organisms), and in situ (natural context) methodologies utilized.

DNA AS THE GENETIC MATERIAL

  • Griffith's transformation experiments indicated DNA’s role in heredity.
  • Avery, MacLeod, and McCarty’s work isolated the transforming substance as DNA.
  • Hershey and Chase’s experiments confirmed DNA as the genetic material using bacteriophages.

DNA STRUCTURE DISCOVERIES

  • Chargaff's base pairing rules (A=T, C=G), later confirmed by Watson and Crick.
  • Rosalind Franklin's x-ray diffraction contributed to the understanding of the DNA double helix.

GENETIC MATERIAL FUNCTIONS

  • DNA serves as a long-term information repository, while RNA acts as a transient messenger.

SUMMARY OF DIMENSIONS AND SIZES

  • Human genome comprised of approximately 3.2 billion base pairs and organized into 23 pairs of chromosomes.
  • Variability in genome sizes and chromosome counts across different species, with no direct correlation to evolutionary complexity.