BIO273 Biology - History of the Nucleus PDF

BIO273 Biology History of the Nucleus Epigenesis  Process by which plants, fungi & animals develop from a seed, spore or egg through a sequence of steps in which cells differentiate & organs form Proposed by Aristotle (384-322 BC)  Creationist theories of life’s origin prevented...

BIO273 Biology History of the Nucleus Epigenesis  Process by which plants, fungi & animals develop from a seed, spore or egg through a sequence of steps in which cells differentiate & organs form Proposed by Aristotle (384-322 BC)  Creationist theories of life’s origin prevented its acceptance SCHOOL OF BIOLOGICAL SCIENCES 2 AND APPLIED CHEMISTRY Preformation  Theory that an embryo develops from a complete miniature version of the organism All organisms were created at the same time Succeeding generations grow from homunculi or animalcules These have existed since the beginning of creation  Homunculi had their own sperm & so forth Adam had sinned; therefore, all had sinned  Explanation for conception Man the seed, woman the incubator Why did children resemble their mothers? SCHOOL OF BIOLOGICAL SCIENCES 3 AND APPLIED CHEMISTRY Microscopy  1671 Antonie Van Leeuwenhoek Dutch draper – small lenses for cloth inspection First to make & use real microscope with superior single lenses (270X) Expert at creating high quality lenses Saw things no one had ever seen before (animalcules) Discovered the world of the microbes - “Father of Microbiology” SCHOOL OF BIOLOGICAL SCIENCES 4 AND APPLIED CHEMISTRY Discovery of the Nucleus  1831 Robert Brown Scottish Botanist Microscopes with improved lenses Observed plant cells Discovered the Nucleus Called it a “Nucleus” after Latin “Nucula” for little nut SCHOOL OF BIOLOGICAL SCIENCES 5 AND APPLIED CHEMISTRY The Nucleus Discovery of Function  Fertilization studies (1870s) Sperm cell + Egg cell = Zygote Zygote = first cell of a new organism  Sperm contains very little cytoplasm Nucleus with a tail  Conclusion Nucleus must contribute some information to create a new organism SCHOOL OF BIOLOGICAL SCIENCES 6 AND APPLIED CHEMISTRY Fertilization  Oscar Hertwig (1875)  Sea Urchins – External fertilization & development  Observations Penetration of the of the sperm into the egg cell Once on sperm entered, egg prevented any others Sperm Nucleus & Egg Nucleus fuse minutes later  Embryo develops into an individual with a mixture of parental traits  Conclusion Nuclei of both egg & sperm contribute the hereditary material SCHOOL OF BIOLOGICAL SCIENCES 7 AND APPLIED CHEMISTRY The Nucleus Discovery of Function  Theodor Boveri (1889)  Sea Urchins – External fertilization & development  Species A (enucleated eggs) Shake eggs until broken open & nucleus removed  Species B Obtain the sperm (nucleus)  Add sperm from B to enucleated eggs from A Always developed into species B  Conclusion The Nucleus determines the characteristics of the organism SCHOOL OF BIOLOGICAL SCIENCES 8 AND APPLIED CHEMISTRY The Nucleus Discovery of Function  Joachim Hammerling (1943)  Acetabularia – large unicellular alga (2 – 5 cm tall) Consist of a cap, stalk & base (contains nucleus) Different species = different cap  Remove the cap – will regenerate from the base SCHOOL OF BIOLOGICAL SCIENCES 9 AND APPLIED CHEMISTRY The Nucleus Discovery of Function  Graft cap on to base from a different species  Cap that develops always shows the shape of the base species  Conclusion Nucleus controls the development of the cell SCHOOL OF BIOLOGICAL SCIENCES 10 AND APPLIED CHEMISTRY Summary  Nucleus controls the functions & development of the cell  Nuclei from sperm & egg fuse at fertilization to create zygote  The hereditary material is in the Nucleus SCHOOL OF BIOLOGICAL SCIENCES 11 AND APPLIED CHEMISTRY