Molecular Bio Exam #1

Chapter 1: Introduction to Molecular Biology

1. History of Molecular Biology

   • Important events:

     • Meischer: Discovered nuclein (now known as DNA).

     • Morgan: Linked genes to chromosomes using fruit flies.

     • Beadle & Tatum: Proposed the "one gene, one enzyme" hypothesis.

     • Griffith: Demonstrated bacterial transformation.

     • Avery, McCarty & MacLeod: Proved DNA as the transforming principle.

     • Hershey-Chase: Showed that DNA is the genetic material in viruses.

     • Watson & Crick: Developed the double helix model of DNA.

2. Characteristics of Living Systems

   • All living organisms:

     • Require energy.

     • Maintain homeostasis.

     • Exhibit growth and reproduction.

     • Are made of cells and have genetic material (DNA or RNA).

3. Universal Flow of Genetic Information (Central Dogma)

   • DNA → RNA → Protein.

   • Exceptions: Retroviruses (e.g., HIV) use reverse transcription (RNA → DNA).

4. Key Experiments

   • Meischer: First identified DNA (called it nuclein).

   • Griffith: Showed bacterial transformation.

   • Avery, McCarty & MacLeod: Proved DNA was the substance causing transformation.

   • Hershey-Chase: Used bacteriophages to show DNA was genetic material.

   • Beadle & Tatum: Established that genes code for enzymes.

5. Franklin, Todd, Watson & Crick and the DNA Double Helix

   • Rosalind Franklin used X-ray diffraction to image DNA.

   • Watson & Crick: Proposed the double helix structure.

   • Maurice Wilkins assisted with DNA structure studies.

6. Key Figures in Discovering DNA/RNA & Central Dogma

   • Crick coined "central dogma" and proposed the flow of genetic information.

   • Nirenberg & Matthaei: Cracked the genetic code.

7. RNA World Hypothesis

   • RNA was the original molecule for storing genetic information and catalysis.

   • Evidence: Ribozymes (RNA molecules with catalytic activity).

8. Key Definitions:

   • Catalysis: The process of speeding up a reaction.

   • Enzyme: Proteins that act as biological catalysts.

   • Horizontal Gene Transfer: Transfer of genes between organisms (not parent to offspring).

   • Retrovirus: Viruses that reverse transcribe RNA into DNA.

   • Last Universal Common Ancestor (LUCA): Hypothetical early cell from which all life descends.

9. Scientific Method:

   • A systematic process involving hypothesis generation, experimentation, observation, and conclusion.

10. Model Organisms:

    • Organisms (e.g., mice, fruit flies) used for studying biological processes due to shared characteristics with humans.

Chapter 2: Mendelian Genetics

1. Mendelian Genetics Terminology

   • Homozygous: Having two identical alleles.

   • Heterozygous: Two different alleles.

   • Genotype: Genetic makeup.

   • Phenotype: Observable traits.

   • Alleles: Variations of a gene.

   • Diploid: Two sets of chromosomes.

   • Haploid: One set of chromosomes.

2. Mendel's Experiments

   • Law of Segregation: Alleles segregate during gamete formation.

   • Law of Independent Assortment: Genes for different traits are inherited independently (holds only for unlinked genes).

3. Non-Mendelian Genetics

   • Incomplete dominance: Intermediate phenotype (e.g., red and white flowers produce pink offspring).

   • Codominance: Both alleles expressed (e.g., AB blood type).

   • Polygenic inheritance: Traits controlled by multiple genes (e.g., skin color).

4. Mitosis & Meiosis

   • Mitosis: Produces two identical diploid cells.

   • Meiosis: Produces four genetically unique haploid cells; involves crossing over and independent assortment.

5. Gene Linkage

   • Genes close together on the same chromosome are inherited together.

   • X-linked traits: Traits associated with genes on the X chromosome.

6. Genetic Mapping

   • Crossing over: Exchange of genetic material between homologous chromosomes.

   • Genetic markers: Help identify locations of genes on a chromosome.

7. Mutations & Recombination

   • Mutation: A change in DNA sequence that can lead to genetic variability.

   • Recombination: The rearrangement of genetic material.

8. Clinical Correlations

   • Sickle Cell Anemia: Caused by a mutation in hemoglobin gene.

   • Huntington’s Disease: Caused by expansion of CAG repeats in a gene.

Chapter 3: Molecular Interactions and Thermodynamics

1. Chemical Bonds & Biological Interactions

   • Covalent bonds: Strong bonds where electrons are shared.

   • Hydrogen bonds: Weak interactions, important in DNA and protein structures.

   • Van der Waals forces: Weak, non-covalent interactions.

2. Thermodynamics in Biology

   • Gibbs Free Energy (ΔG): Determines if a reaction is spontaneous.

     • ΔG < 0: Spontaneous (exergonic).

     • ΔG > 0: Non-spontaneous (endergonic).

   • First Law of Thermodynamics: Energy cannot be created or destroyed.

   • Second Law of Thermodynamics: Entropy (disorder) increases in an isolated system.

3. Enzymes and Activation Energy

   • Enzymes lower the activation energy of reactions, speeding them up.

4. ATP in Biological Systems

   • ATP hydrolysis releases energy used to drive cellular processes (e.g., protein synthesis, DNA replication).

5. Energy in Bonds

   • Different types of bonds store different amounts of energy, with high-energy phosphate bonds in ATP being crucial for cellular work.