Bacterial Genetics

• Concept of DNA was already being applied by farmers through selective breeding

  8000 BC
• Charles Darwin published the Theory of Evolution


  1859
• Gregor Mendel first documents hereditary traits in garden peas


  1863
• James Watson, Francis Crick, and colleagues first described the molecular structure of DNA


  1953

  
• Genetic code is revealed. Established that a sequence of 3 nucleotide bases corresponds to each of the 20 amino acids in protein production

  1966
• DNA composition of humans is 99% similar to chimpanzees and gorillas

  1972
• Human Genome Project (HGP) is launched


  1990
• HGP was completed


  April 2003
• Biochemist Frederick Sanger developed a rapid DNA sequencing technique (Sanger method)


  1977
• Huntington's Disease was first genetic disease to be mapped using DNA sequencing


  1983
• Kary Mullis invented the polymerase chain reaction (PCR) technology for amplification of DNA


  1983
• Genetics


  Study of the mechanisms by which traits are passed from one organism to another
• Genome


  Refers to all the genes in a particular organism
• Genes


  Unit of heredity transferred from a parent to offspring
• Chromosomes


  Cellular structure that is discrete and composed of a neatly packed DNA molecule, which physically carries hereditary information

  
• Eukaryotic Chromosome


  Located in the nucleus, can occur in singles or pairs, linear, DNA molecules are tightly wound around histone proteins

  
• Bacterial Chromosome


  Called "genophores", double-stranded DNA molecules that are enclosed in a giant loop, organized in nucleoid, tethered to the plasma membrane, circular, secured and condensed by histone-like proteins

  
• Central Dogma of Life


  Describes the flow of genetic information in cells from DNA to mRNA to protein

  
• DNA Replication


  Process of just copying the DNA molecule, one-directional process wherein DNA copies itself, catalyzed by DNA polymerase

  
• Transcription


  Process of synthesizing RNA from a specific DNA segment using the enzyme, RNA polymerase, only one DNA strand is being transcribed, bidirectional process

  
• Translation


  Once the RNA is synthesized, it is then converted to proteins through the process of translation, ribosomes aid in the process, translation is used to translate in a different language

  
• Frederick Griffith


  Tried to develop a vaccine for pneumonia, studied 2 strains of Streptococcus pneumoniae: S (pathogenic; deadly) and R (non-pathogenic)
• Frederick Griffith's Experiment


  The material in dead bacterial cells can genetically transform living bacterial cells

  
• Oswald Avery


  Tried to discover a way to counter the virulence of Diplococcus pneumoniae in 1944, found out that the transforming factor was DNA
• Alfred Hershey and Martha Chase's Experiment


  Did experiments in 1952 to determine the composition of the genetic material of a bacteriophage
• Erwin Chargaff's Experiment


  Discovered 2 rules which led to the discovery of the double helix DNA structure: 1) Base pair make up of DNA, 2) DNA could be the genetic material

  
• There has always been a competition on who will report first or who will discover first: 1) What is the structure of the DNA molecule? 2) How could a molecule carry in code the entire design specifications for a living organism?
• King's College, London


  Maurice Wilkins and Rosalind Franklin
• Cambridge University


  Francis Crick and James Watson
• Watson and Crick came up with a chemically stable model of DNA

  
• Wilkins and Franklin contributed images that provided important/key evidence for elucidating the structure of DNA
• Chargaff was the one who raised the point of complementary base pairing
• There has always been a competition on who will report first or who will discover first
• Groups of researchers who tried to answer these questions


  • King's College, London: Maurice Wilkins and Rosalind Franklin
  • Cambridge University: Francis Crick and James Watson
• Rosalind Franklin


  Studied the X-ray Diffraction technique in Paris, then transferred to the laboratory of Maurice Wilkins, an expert in Crystallography
• In May 2, 1952, Wilkins, Franklin, and Gosling took an X-ray diffraction photo of DNA
• The X-ray diffraction photo was used to look at the dimensions of the DNA strands with phosphatases on the outside of a seemingly helical structure
• Watson and Crick produced paper cut-outs of bases A, C, T, and G, and metal scraps from a machine shop to make a model of the helical structure of DNA
• Watson and Crick discovered that DNA has a double helix with sugars and phosphates forming the outer strands of the helix, with the bases pointing into the inner center

  
• Watson and Crick received a nobel prize for this model