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Darwininan Theory of Evolution
This disproved spontaneous generation by stating:− Within a population there exists genetic variation− Those individuals possessing inheritable features best suited to the environment will survive and reproduce− In coverse situations, organisms not closely related that are subjected to similar environments should possess similar adaptations -
Mendel's pea plant experiments show the inheritance of genes
He examined flower colour (purple or white), flower position, seed colour (yellow or green), seed shape (round or wrinkled), pod shape (inflated or constricted), pod colour (green or yellow), stem height (tall or short).Mendel worked with homozygous plants, and crossed them with heterozygous plants (to make the F1 generation. He found that only the dominant genes were present (then called factors), and when crossed again, he found the dominant: recessive genes in a 3:1 relationship -
Pasteur published his findings on the spoiling of food due to microbes and was the first to vaccinate
Pasteur proved that food goes bad because of microbes, and that sterilising could prevent it (through his meat broth experiment). He demonstrated that the souring of milk was due to the action of certain bacteria and the bi product of respiration of these bacteria. He developed the pasteurisation process by heating the wine to 60oc, denaturing the enzymes.Vaccinated 25 sheep and left 25 unvaccinated then gave all lethal doses of anthrax. 25 vaccinated survived. -
Koch published his postulates and identified anthrax as bacteria
Koch's postulates
1. Organism suspected of causing the disease must be present in all organisms that have the disease2. A pure culture of the organism is suspected of casing the disease must be obtained. All other organisms must be excluded from the sample3. A healthy organism must be inoculated with the pure culture and the potential host must present the same symptoms.4. The suspect organism must be reisolated, recultured and identified -
Sutton and Boveri demonstrate the behavoiur of chromosomes and explaned the inheritance of genes
Boveri - Sea urchins. Discovered that chromosomes occur in pairs and that a full set is needed for organisms to develop properly
Sutton - Grasshoppers. Homologous pairings, genes must be located on chromosomes since there were more inheritable characteristics than chromosomes. -
Morgan discovered sex linkage
Studied fruit flies and noticed that the males carried more of the recessive allele than females -
Beadle and Tatum develop the one-gene, one- protein hypothesis
Hypothesis stated that each biochemical cellular reaction was controlled by one enzyme and also by one gene, however, we now know that there are mulitple proteins in a polypeptide, the factor that controls genes. Therefore, the theory has been amended to 'one-gene, one -polypeptide' -
MacFarlane Burnett discovers memory cells and developed an influenza vaccine
Frank Macfarlane Burnett studied immunology and worked on the development for an influenza vaccine, identified strains of swine flu in Australia, published papers on the variation of virulence of influenza as well as calculated mutation rates.Specific studies and development of techniques to understand viruses also led MacFarlane Burnet to begin our understanding of the immune system. Burnet concluded that a human immune system contained un-activated B cells that could be activated and produce -
Watson, Crick, Wilkins and Franklin discovered the structure of DNA
Through the combined efforts of these four scientists, the structure of DNA was discovered and published
Watson and Crick - model builders
Franklin - xray crystallographer
Wilkins - Extracted fibres from a gel form of DNA and gave phtotograph to Watson and Crick