Lecture 3: Intro to Molecular Biology

Introduction to Life and Genetics

• Understanding the definitions and concepts of life is essential for diving deeper into molecular biology and genetics.

• Genetics and molecular genetics are intricately interconnected, forming the foundation for biological sciences.

Defining Life

• Question: What is life? An attempt to encapsulate this leads to complexity.

  • Dictionary Definition: Life is often defined as the ability to grow or change.

  • Critique: This definition appears incomplete because it does not encompass all aspects of life.

• Key Characteristics of Life:

  • Growth and Reproduction: Life involves the capacity to grow and reproduce, illustrating the cycle of life.

  • Consumption of Nutrients: Living organisms take in nutrients, transforming them into usable energy (e.g., humans consuming food).

  • Information Content: Living cells contain information necessary for reproduction and nutrient transformation.

Complexity of Life

• Life must embody complexity, which includes the ability to adapt to its environment.

• The ability to respond to stimuli is crucial, exemplified by organisms adjusting their behaviors based on environmental changes.

• Counterexample: Non-living entities like crystals can grow and respond to stimuli but are not considered alive due to the lack of true biological complexity and requirements.

Biological Requirements

• To apply a more definitive definition of life, a biological element must be included:

  • Biological Elements: The presence of specific biological requirements delineates living organisms from non-living matter.

• These requirements include essential macromolecules that make up all living cells.

Macromolecules of Life

• Life is primarily constituted by six essential atoms:

  • Carbon (C), Hydrogen (H), Nitrogen (N), Oxygen (O), Phosphorus (P), Sulfur (S).

• Four major macromolecules are fundamental to all living organisms:

  1. Carbohydrates: Basic units are sugars (e.g., glucose); crucial for energy storage and providing structural support within cells.

  2. Lipids: Basic units include fatty acids; essential for energy storage, cell membrane structure, and insulation.

  3. Nucleic Acids: Basic units are nucleotides; DNA and RNA serve as the blueprint for genetic information and protein synthesis.

  4. Proteins: Basic units are amino acids; they perform a myriad of functions in the body, making up tissues and acting as enzymes involved in biochemical reactions.

Summary of Macromolecules

• Carbohydrates:

  • Composed solely of C, H, O.

  • Important for energy storage and structural purposes.

• Lipids:

  • Comprised of fatty acids, stored as energy, and essential for the integrity of cell membranes.

• Nucleic Acids:

  • DNA and RNA are made of nucleotides containing C, H, O, phosphorus, and nitrogen.

  • Crucial for genetic information storage and transmission.

• Proteins:

  • Made of 20 amino acids (with nitrogen and sometimes sulfur); involved in diverse cellular functions—from structural roles to enzymatic activity.

The Historical Context of Molecular Genetics

• Recognition of proteins and nucleic acids as biological macromolecules spanned from the 17th century onwards:

  • Prominent Figures:

    • Friedrich Miescher isolated nucleic acid (1838).

    • Franklin and Watson discovered DNA structure (mid-20th century).

  • Various experiments established the central dogma: DNA -> RNA -> Protein.

Key Experiments in Genetics

• Griffith's Experiment (1928):

  • Demonstrated the phenomenon of bacterial transformation, providing early insight into heredity.

• Avery's Research (1944):

  • Showed that DNA was the transforming substance responsible for heredity.

• Hershey-Chase Experiment (1952):

  • Confirmed through bacteriophage studies that DNA is the genetic material.

Applications of Molecular Genetics

• Advancements in biotechnology enable the cloning of genes and the production of biological products, including:

  • Insulin production, gene therapy, and DNA diagnostics:

    • Examples include using recombinant DNA technology to mass-produce insulin and other pharmaceuticals.

• Agricultural Applications:

  • Development of genetically modified organisms (GMOs) for better crop protection and yield (e.g., herbicide-resistant plants).

Closing Thoughts

• The overlapping fields of molecular biology, genetics, and biotechnology reshape our understanding and applications of life sciences. The frame of reference for defining and understanding life must include the complexity and biological requirements detailed above.