151 lec 9 bacte gmr 1

• 8000 BC: Concept of DNA was already being applied by farmers through selective breeding


  Crops or animals with desirable features were selected and bred to have future generations of organisms with good qualities
• 1859: Charles Darwin published the Theory of Evolution

  • Evolution through natural selection
  • Was not widely accepted during his time; was only accepted after his death
• 1863: Gregor Mendel first documents hereditary traits in garden peas

  • An Augustinian monk
  • Cross-bred peas of different varieties and characteristics (e.g. height, color, pod and seed shape, flower position, etc.)
  • Further developed concept of heredity and DNA
• 1953: James Watson, Francis Crick, and colleagues first described the molecular structure of DNA

  • DNA’s “double helix” structure
  • From then on, there were other developments in our knowledge of DNA
• Other discoveries

  • 1966: Genetic code is revealed. Established that a sequence of 3 nucleotide bases corresponds to each of the 20 amino acids in protein production.
  • 1972: DNA composition of humans is 99% similar to chimpanzees and gorillas.
  • 1990: Human Genome Project (HGP) is launched – an international collaborative effort to sequence the entire human genome.
• April 2003: HGP was completed.

  • Gave us a complete genetic blueprint of humans
  • Revealed the location of around 30,000 human genes. (This number is currently being debated by scientists who suggest the number is closer to 70,000.)
• OTHER IMPORTANT DATES AND PERSONALITIES

  • 1977: Biochemist Frederick Sanger developed a rapid DNA sequencing technique (Sanger method); Received Nobel Prize in chemistry in 1980
  • 1983: 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; received Nobel Prize in Chemistry in 1993
• Genetics

  • Study of the mechanisms by which traits are passed from one organism to another
  • How different traits can be passed from parents to offspring
  • Examples: Black hair, nose shape, body type and build, etc.
  • Science of heredity
  • Study of the structure and function of genetic material
  • Study of the expression and variation of traits
  • Siblings can exhibit different traits even if they have the same parents
  • Study of how genetic material varies/changes (mutations)
• Genome

  • Refers to all the genes in a particular organism
  • Contains all genetic information of the cell
  • Found mostly in the chromosomes
  • But for others, it can be found in non-chromosomal sites
  • Important in sequencing and molecular characterization of genes
• Genes

  • Also known as the ‘molecules of life’
  • Unit of heredity transferred from a parent to offspring
  • Specific sequence of bases that controls the specific characteristics of the body
  • 20th Century: Genes are located in the chromosome
  • 1880: Genes are made up of deoxyribonucleic acid (DNA)
  • Prior to this, people thought that DNA was made up of proteins only
  • 1880: Chromosomes are reported to be made up of protein and DNA
• Chromosomes

  • Cellular structure that is discrete and composed of a neatly packed DNA molecule, which physically carries hereditary information
  • Packed with proteins and DNA
• Eukaryotic Chromosome

  • Located in the nucleus
  • Can occur in singles or pairs
  • Linear
  • DNA molecules are tightly wound around histone proteins
  • For eukaryotes, chromosomes contribute to the set of gametes in each parent and ensure variation of genetic diversity of offspring
• Bacterial Chromosome

  • Called “genophores”
  • Double-stranded DNA molecules that are enclosed in a giant loop
  • Organized in nucleoid; tethered to the plasma membrane
  • Less sequence-based structure than eukaryotes, i.e. less organized
  • Circular
  • Secured and condensed by histone-like proteins
  • In prokaryotes, chromosomes are not engaged in sexual union with other bacteria because they produce asexually through binary fission
  • Daughter cells are exact genome copies of mother
  • bacteria / cell
• Central Dogma of Life

  • Describes the flow of genetic information in cells from DNA to mRNA to protein
  • In these processes, genes in the DNA sequence are transcribed into messenger RNA (mRNA) which will then be translated into proteins
  • Steps:
  • Replication
  • Transcription
  • Translation

  
• DNA Replication

  • Process of just copying the DNA molecule
  • One-directional process wherein DNA copies itself
  • Catalyzed by DNA polymerase
  • This process must first occur before a cell can produce two genetically identical daughter cells
• Transcription

  • Means transcribing or copying in the same language
  • Process of synthesizing RNA from a specific DNA segment using the enzyme, RNA polymerase
  • Only one DNA strand is being transcribed
  • Bidirectional process
  • DNA to RNA = Transcription
  • RNA to DNA = Reverse Transcription
  • Occurs at the nucleus
• Translation


  1. RNA synthesis

  2. Conversion to proteins
• Ribosomes


  Aid in the process of translation
• In Transcription


  It is "transcribed in the same language"
• In Translation


  It is used to translate in a different language
• Translation


  • When you are in an international conference and there are many international guests, someone translates the convention into different languages
• In eukaryotes (animals and humans)


  • Translation and transcription are separated from each other, i.e. one process must first be finished before another can proceed
• In prokaryotes


  • They can translate an RNA molecule into proteins even before transcription has ended, i.e. processes can occur simultaneously
• Genomics


  DNA replication, DNA damage, DNA repair, etc. or DNA structure

  
• Transcriptomics


  Structure, types, genetic material, composition of RNA

  
• Proteomics


  Study of proteins

  
• Metabolomics


  study of metabolomes

  
• Frederick Griffith

  • Tried to develop a vaccine for pneumonia
  • January 1928: He reported the Griffith’s experiment
  • Studied 2 strains of Streptococcus pneumoniae:
  • S (pathogenic; deadly)
  • R (non-pathogenic)

  
• Frederick Griffith's Experiment


  Discovered the transforming factor while working on the rough and smooth strains of Streptococcus pneumoniae
• Streptococcus pneumoniae strains

  • Smooth strain is the deadly / pathogenic strain
  • Rough strain is the nonpathogenic strain
• 1st experiment


  1. Injected the rough and smooth strains separately in two mice

  2. S strain caused illness or death in the experimentally infected mouse

  3. Mice injected with the rough strain survived the infection

  4. Recovered the bacteria from the mice that died from infection

  5. No procurable bacteria specimens from the mice that survived
• 2nd experiment


  1. Heat killed the smooth strain of the Streptococcus pneumoniae

  2. Injected the smooth strain into mice

  3. Injected mice survived

  4. No illness observed

  5. No bacterial cells isolated from the heart of the infected mice
• 3rd experiment


  1. Heat killed the smooth strain and mixed it with live rough strain of Streptococcus pneumoniae

  2. Injected mice fell ill and died

  3. Recovered the S strains from the mice

  4. Rough strain was converted into smooth strain

  5. Live R and S cells found in the blood and heart of the mice
• There was material from the harmful but dead bacterial S strain that was transferred to the R strain
• There was a chemical substance from one cell that is capable of genetically transforming another cell
• Oswald Avery


  Scientist who conducted experiments to discover the transforming factor in Diplococcus pneumoniae
• Avery tried to discover a way to counter the virulence of Diplococcus pneumoniae


  1944
• Avery followed the work of Griffith
• Transforming factor


  Chemical substance responsible for transforming the heat-killed S strain to be a pathogenic S strain again
• Griffith did not know what the transforming factor was