History

• Preformationism (Pythagoras and Aristotle) - until 17th Century

  It was believed that the reproduction of organisms originate through formation of

  "miniature versions known as homunculus" of themselves.
• Each part organ of the body can produce

  "gemmules" that contribute to the

  formation of an offspring.
• The idea of Preformationism originated from the insects, amphibians and reptiles - (known today as parthenogenesis) that allows them to reproduce without sexual interaction.
• • Spermists: sperm contains the miniature individual and only nourished by the ovum.
• Ovists: thought the same and that the seminal fluid only stimulates it.
• Since earlier civilizations are patriarchal, the widespread accepted idea is of the spermists.
• Epigenesis (William Harvey) - 1651

  William Harvey (popular ovist)

  criticized Aristotle's work by asserting "ex ovo omnia", which states that all organisms come from eggs.
• Although William Harvey’s idea become widespread among intellectualists (Descartes, Galileo and Copernicus), his assumptions were considered only theoretical and lacks observational data.
• Microscopy (Robert Hooke and

  Antoine van Leeuwenhoek) - 1655 and 1677

  As the invention of Robert

  Hooke of simple microscope rose popularity, he was able to discover and coin the term "cell' from cell wall of plant cells.
• Meanwhile, Leeuwenhoek was able to observe sperm cells by staining it using saffron flowers. Hence, the safrain stain.
• Theory of Use and Misuse and Theory of Acquired Characteristics (Jean Baptiste De Lamarck) - 1802
• Theory of Use and Misuse: The organs of an organism that is frequently and continuously used becomes more developed and prominent across the lifetime of an individual.
• On the other hand, organs that does not elicit frequent and continued use will be weak and deteriorated across the lifetime of individual.
• Theory of Acquired Characteristics: The modifications that an organism underwent in its life due to the factors of use and misuse will be preserved and will be passed on to the next generation.
• Theory of Evolution by Natural Selection

  (Charles Darwin) - 1859
• Theory of Evolution of Natural Selection: all organisms even they belong in the same species, there will be changes in their characteristics due to pressure exerted by the environment.
• Germplasm Theory (August Weismann) - 1892

  As the field of microscopy developed, Weismann has postulated that there are two types of cells in the body:

  • (Autosomal) Somatic Cells: responsible for sustaining the body
  • Gametes- contains hereditary information
• Weismann also disproved the concept of preformation using 22 pairs of mice, that shown even the tails of parents are cut (all offspring have grown tails)
• The role of DNA in heredity was first worked out by studying bacteria and the viruses that infect them.
• Griffith’s Experiment (1928) called the phenomenon transformation now defined as a change in genotype and phenotype due to the assimilation of external DNA by a cell
• Rosalind Franklin (1952) produced a picture of the DNA molecule using x-ray crystallography, thus proving DNA contains hereditary information
• Gregor Johann Mendel is not a pioneer in genetic modification in organisms.
• In Mendel’s university, similar scientists that are ahead of him such as Karl Nestler has already performed hybridization in sheep.
• However, Mendel was chosen to study hybridization and chose pea plants to study.
• Peas were a staple food in Czech republic that is why good crop yield is essential to the monastery.