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HEREDITY

HEREDITY. Preformation. Epigenesis. Assembled Each person is put together by contributions of each parent The adult develops from an amorphous mass Came from Pythagoras and Aristotle. Pre-existing All people who will be born have been formed The homunculus unfolds to form the adult

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HEREDITY

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  1. HEREDITY

  2. Preformation Epigenesis Assembled Each person is put together by contributions of each parent The adult develops from an amorphous mass Came from Pythagoras and Aristotle • Pre-existing • All people who will be born have been formed • The homunculus unfolds to form the adult • Came from Egyptian alchemy

  3. Preformation • More in line with western Christianity • Leeuwenhoek and other early microscopists claimed to have seen the homunculus

  4. Epigenesis • Later microscopists noted that certain tissues, like the apical meristems of plants, were made of a region of identical cells that developed into typical plant tissues. • William Harvey (1578-1657, England) stated that all animals came from eggs and they were fertilized by transference of hereditary material from the semen.

  5. Pangenesis • Charles Robert Darwin (1809-1882, Britain) • Hereditary particles from all parts of the body are transported by the circulatory system and concentrated in the gametes. • It began to take on a Lamarkian perspective and explain evolution by acquired characters • Attempted to be confirmed by Francis Galton (1822-1911, Britain). Disproved

  6. Germ Plasm Theory • Friedrich Leopold August Weismann (1834-1914, Germany) • Hereditary particles retained only if needed as development progresses in somatic cells, but remains unchanged in germ plasm ~disproved by cloning.

  7. Hugo de Vries • Modified pangenesis • Called particles pangenes (shortened to genes later) • Working on Evening Primrose noticed flower color either white or yellow in particular ratios • Developed mutation theory of evolution • In 1900 discovered papers published 30 years earlier by Gregor Johann Mendel • Also discovered by Carl Correns (1864-1933, Germany) and Erich von Tschermak (1871-1962, Austria)

  8. Gregor Johann Mendel • 1822-1884, Austrian Empire (now Czech Republic) • Joined Augustinian Order and took name Gregor • Studied physics under Doppler • Failed teaching exam (oral portion) and became an administrator of monastery of Brünn (Brno in Czech) • Became interested in heredity and began to study mice but abbot uncomfortable having a monk who studied sex; so, Mendel began to study peas and looked at 7 traits that seemed to be independent of each other.

  9. Communicated with Carl Wilhelm von Nägeli (1817-1891, Switzerland). • Theory of ideoplasm (a portion of the cytoplasm that carried hereditary information) • Commented to Mendel: ‘your paper is of some interest but is too empirical to be importantto the science of heredity’. • Advised him to work on animals instead

  10. Law of Segregation  Dominant and recessive phenotypes.(1) Parental generation.(2) F1 generation.(3) F2 generation. Dominant (red) and recessive (white) phenotype look alike in the F1 (first) generation and show a 3:1 ratio in the F2 (second) generation.

  11. Law of Independent Assortment Dihybrid cross. The phenotypes of two independent traits show a 9:3:3:1 ratio in the F2generation. In this example, coat color is indicated by B(brown, dominant) or b (white), while tail length is indicated by S (short, dominant) or s (long). When parents are homozygous for each trait (SSbbandssBB), their children in the F1 generation are heterozygous at both loci and only show the dominant phenotypes. If the children mate with each other, in the F2 generation all combinations of coat color and tail length occur: 9 are brown/short (purple boxes), 3 are white/short (pink boxes), 3 are brown/long (blue boxes) and 1 is white/long (green box).

  12. Genes and Chromosomes • WalterStanboroughSutton (1877-1916, USA) • Noted that the segregation and independent assortment of grasshopper chromosomes during meiosis conformed to Mendel’s Laws (1900-1903) • Thus Genes must be located on the chromosomes • Theodor Heinrich Boveri (1862-1915, Germany) independently came to the same conclusion

  13. Chromosomes and Fruit Flies • T. H. (Thomas Hunt) Morgan (1966-1945, USA) • Began to study mutations in fruit flies after rediscovery of Mendel’s Laws • Sought out mutant forms • Discovered sex-linked traits and began to map chromosomes by cross-over distance

  14. Mutations and Fruit Flies • H. J. (Hermann Joseph) Muller (1890-1967, USA, USSR, Britain) • Followed Morgan and worked on fruit flies • Induced mutations by high temperature, X-rays

  15. What is the gene made of? • Oswald Theodore Avery (1877-1955, Canada, USA) • Showed that DNA moved from one bacterium to another could transform a benign strain to a virulent strain in 1940s

  16. Hershey and Chase (1952) Alfred Day Hershey (1908-1997, USA) and Martha Cowles Chase (1927-2003, USA)

  17. Structure of DNA (1953) • James Dewey Watson (1928-, USA) • Francis Harry Compton Crick (1916-2004, Britain & USA • Maurice Hugh Frederick Wilkins (1916-2004, New Zealand & Britain) • Rosalind Elsie Franklin (1920-1958, Britain)

  18. Central Dogma of Molecular Biology • Francis Crick (1958) • Sequence of information transfer

  19. Decoding DNA • Marshall Warren Nirenberg (1927-2010, USA) • Began to perform simple (conceptually) experiments to generate polypeptides by using RNA sequences of • UUU… (generated poly phenylalanine) • AAA…(generated poly lysine) • CCC…(generated poly proline)

  20. The Codon George Gamow proposed that 3 bases would serve to unambiguously code for the 20+ different amino acids to code for particular polypeptides

  21. HIV and Reverse Transcriptase

  22. Polymerase Chain Reaction Developed in 1983 by Kary Banks Mullis (1944, USA)

  23. Genome Sequencing • John Craig Venter (1946, USA) • Employed shotgun method to sequence DNA with private company in competition with the Human Genome Project • Long chains broken randomly • Small pieces sequenced • Then small sequences reassembled • Method brought Human Genome Project in years ahead of schedule and billions under budget. • Known recently for creating artificial life with assembled genome. Whole Genome Shotgun Sequencing Hierarchical Shotgun Sequencing

  24. Human Genome Project • James Watson was the first director (1988-1992) • Human genome has ~20,500 genes • International effort begun in 1980s using PCR • Strong effort begun in 1990 • Separate genome into pieces ~150,000bp and sequence • Look for start/stop codes • 1st draft published 2000 • Completed genome 2003 • By 2009, a personal genome could be completed for less than $2,000

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