BIO 101 - Module 1

• REDUCTIONISM - postulates that all biological phenomena can be explained by the laws of chemistry and physics, i.e. explanation of processes can be reduced to the level of atoms and molecules.
• Reductionism is Contrasted with HOLISM (The whole is greater than the sum of its parts) - more applicable in Cell Biology, but today even cell processes are amenable to molecular explanations.
• Similar with Reductionism, MECHANISM was a philosophy that life can be best understood by dissecting parts of the whole (machine, organism, cell), i.e., involves understanding the little parts which makes the whole (machine) work.
• Much earlier, VITALISM was a belief in a “driving force” (vital force; soul) for every living thing, including animals and plants; difficult, if not impossible to prove scientifically
• Two roots of molecular biology: Microbial Genetics and Biochemistry
• BIOCHEMISTRY is referred to as the structural root. This tackles the properties and functions of biomolecules.
• MICROBIAL GENETICS is referred to as the informational root. This deals with information stored in the genetic material and how it is expressed and transmitted. Early experiments in genetics used “simple” systems like bacteria and viruses.
• Definition of molecular biology

  • WILLIAM ASTBURY (1945) coined the term “molecular biology” and defined it as the physical and chemical structure of biological macromolecules
  • the term has been redefined in the present day as: the study of genes and their products and how these function and interact in the organization and perpetuation of living things.
• WILLIAM ASTBURY coined the term “molecular biology” and defined it

  as the physical and chemical structure of biological macromolecules
• Definition of molecular biology

  The term has been redefined in the present day as: the study of genes

  and their products and how these function and interact in the

  organization and perpetuation of living things.
• Logic of Molecular Biology

  1. efficiency
  2. development and evaluation of models
  3. strong inferences
• Efficiency

  -These processes fulfill their specific functions with the least amount of energy and raw materials needed.
• Models

  -which are tentative explanations as to how a system works. This, however, requires further validation by experimentation.
• Arguments are based on data gathered through scientific observations. Arguments and conclusions are therefore based on STRONG INFERENCES.
• 1869 - Fredrick Miescher was the first to characterize and isolate nucleic acids. He described it as an "acidic phosphorus-containing long molecule" which he isolated from pus cells in bloody bandages. He referred to it as “nuclein”.
• 1928- Frederick Griffith performed the transformation experiments on

  two strains of Diplococcus pneumoniae.
• The pathogenic smooth strain (S-type) and the non-pathogenic rough strain (R-type) were injected on mice on four different setups: (a.) the R type alone where the mouse lived, indicative of the avirulence of the R strain, (b.) the S type alone where the mouse died, attributed to the virulence of the strain, (c.) heat killed smooth strain where the mouse lived, indicative of the death or inactivation of the pathogenic agent (d.) rough strain combined with the heat killed smooth strain, both expected to allow the mouse to survive, killed the mouse.
• M.H. Dawson and J.L. Alloway extended the study of Griffith. They precipitated the transforming substance without the need to work on mice. Mixing together heat killed S strain and viable R strains led to the extraction of live S strains from the cell mixture. The process is called In vitro transformation
• 1944 - Ostwald Avery, Colin MacLeod, and Maclin McCarty established the chemical nature of the transforming substance.
• The general properties of the transforming substance were summarized as having a physical viscous silky sheen which loses activity in distilled water, increased acid concentration, and heat. Nitrogen to phosphorus ratio was at 1.67 with UV max absorption at 260 nm.
• Exposure to enzymes which degraded proteins, lipids, and carbohydrates did not inactivate the transforming substance. However, upon exposure to DNAses, the transforming molecule lost its ability to cause virulence. Hence, it was postulated that DNA is the transforming molecule.
• Many scientists disagreed because:

  • DNA is too simple; proteins are more diverse

  • DNA is relevant only to some bacteria; protein is more likely the genetic material.

  • The extract was contaminated/not pure DNA.
• Results of Avery, MacLeod and McCarty's experiment:

  A) Biuret/Million Test

  B) Chloroform/Ethanol Extraction

  C) Orcinol (Bial)

  D) dische diphenylamine

  E) -

  F) -

  G) Weakly +

  H) +

  I) +

  J) +

  K) +

  L) -

  M) +

  
• Alfred Hershey and Martha Chase further established the importance of nucleic acids for the production of new phages and the creation of protein coats for attachment. The process was called the Blender Experiment
• two strains of Diplococcus pneumoniae:

  A) Smooth type

  B) Rough type

  
• T2 Phage

  • Lyses cells after 30-60 mins to release new phages

  • Phages used were labeled

  • Protein coat with 35S

  • DNA with 32P
• Pheobus Levene 


  • DNA is linear

  • made up of nucleotides with four different bases (ATCG)
• Erwin Chargaff, Ernst Fischer and R. Hotchkiss

  • 1 purine : 1 pyrimidine

  • A = T

  • C = G
• Linus Pauling

  • DNA is a triple-stranded molecule
• Maurice Wilkins and Rosalind Franklin 


  • Provided the X-ray diffraction photograph of crystalline DNA
• James Watson and Francis Crick (1953)

  -DNA double helix
• Scope of Molecular Biology:

  1. Genetic Material
  2. Biomolecules
  3. Cellular Structure and Functions
  4. Molecular Basis of Biological Phenomena
• Approaches to Problems

  1. Correlation of Structure and Function
  2. Physical Measurements
  3. In vitro approach