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Mendel’s work and the genes

Mendel’s work and the genes. Eörs Szathmáry (Alpbach 2005). Collegium Budapest. Eötvös University Budapest. Concepts of inheritance. J.B.S. Haldane: „I inherited my watch from my father” „I inherited my nose from father” Geneticists are interested in the latter

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Mendel’s work and the genes

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  1. Mendel’s work and the genes Eörs Szathmáry (Alpbach 2005) Collegium Budapest Eötvös University Budapest

  2. Concepts of inheritance • J.B.S. Haldane: • „I inherited my watch from my father” • „I inherited my nose from father” • Geneticists are interested in the latter • „Genetics deals with the question why organisms that look almost alike are nevertheless different, in a hereditary fashion”

  3. The man and the garden

  4. The plant and the work

  5. Traits chosen by Mendel

  6. Prevention of self-fertilization

  7. Mendelian inheritance • Gametes are always clean! • Stoichiometric paradigm • Probabilistic combinations

  8. Segregation of dominant mutation ½ of the offsping in F2 generation shows dominant phenotype

  9. Segregation of recessive mutation Recessive phenotype appears in 1:3 proportion in generation F2

  10. Two traits together • A concrete count of two segregating traits

  11. Two segregating traits • No linkage • Punnett’s table • Independent combination

  12. Mendel was extremely lucky that his traits are on different chromosomes • Some deviations from Mendel’s rules could not be reconciled in any other way than assuming that they are linked together as “beads on a string” • Morgan has made crosses to analyse linkage • The concept of recombination was later linked to the cytological observation of meiosis (reductive cell division)

  13. The cytology of meiosis

  14. How meiosis is integrated into the plant life cycle

  15. The molecular mechanism of recombination

  16. Whether recombination really occurs depends on the way the Holliday junction is resolved

  17. Whereas genetic recombination can generate variation, its evolutionary role is unclear • Genetic recombination can generate good chromosomes out of partially bad ones • But, unfortunately, the opposite is also true • Something must generate an asymmetry because recombination is “costly”

  18. The compementarity principle

  19. The principle of DNA copying

  20. Genes tend to specify the structure of a protein • Nucleotides sequence of DNA specifies the amino acid sequence of proteins • Proteins can be structural components or enyzmes • “Information: the precise determination of sequence” (Francis Crick)

  21. This shows the genetic code

  22. The genetic code is remarkable

  23. The simplest cells are bacterial

  24. Eukaryotic cells are very complex

  25. Bacterial genes are much simpler than eukaryotic ones

  26. A vast variety of gene products are generated by alternative splicing

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