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Chapter 16: The Molecular Basis of Inheritance

Chapter 16: The Molecular Basis of Inheritance. Important Point:. If you are having trouble understanding lecture material: Try reading your text before attending lectures. And take the time to read it well!. Chromosomes consist of both DNA and Protein

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Chapter 16: The Molecular Basis of Inheritance

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  1. Chapter 16:The MolecularBasis of Inheritance

  2. Important Point: If you are having trouble understanding lecture material: Try reading your text before attending lectures. And take the time to read it well!

  3. Chromosomes consist of both DNA and Protein • DNA was discovered before its role in heredity was understood • People had a sense that chromosomes embodied inheritance before they understood that DNA was the hereditary material • People did not want to believe that DNA was the hereditary material since it is not complex enough • Instead, people believed that proteins must be the hereditary material—they were wrong • Transformation (I.e., Griffith’s experiment, which is mediated by DNA) was discovered before it was understood that it was mediated by DNA The Hereditary Material

  4. Transformation Griffith, 1928

  5. Transforming Principle Sensitivity to DNase Hi, I’m Oswald Avery. I figured out that the transforming principle is DNA! I did this by treating transforming principle with different enzymes, proteases, RNases, DNases… only DNase destroyed its activity Avery, MacLeod, McCarty (1944)

  6. Avery, MacLeod, McCarty (1944) Hi, I’m Theodosius Dobzhanky. I wrote: “Genetics and the Origin of Species” (1937) Hi, I’m Colin M. MacLeod Hi, I’m Maclyn McCarty Colin M. MacLeod, Maclyn McCarty, Detlev Wulf Bronk, Theodosius Dobzhansky, and Wendell M. Stanley Hi, I’m Detley Wulf Bronk. I asked, “Are aliens living among us” (really) Hi, I’m Wendell M. Stanley. I crystalized (and then X-rayed) tobacco mosaic virus!

  7. Erwin Chargaff I made an important observation on the chemistry of DNA

  8. Chargaff’s Rule (1950)

  9. Generalizing beyond Bacteria (sort of) Hershey & Chase, 1952

  10. Hershey & Chase (1952)

  11. I took the first quality X-ray diffraction images of DNA, and am credited with sparking the interests of both Watson and Crick in the question of DNA’s structure Maurice Wilkins (1950) Rosalind Franklin worked under me

  12. Better Pictures of DNA (1951)

  13. We figured it out Watson & Crick (1953) Now we’re famous!

  14. The Double Helix Strand complementarity Strand polarity Antiparallel strands

  15. Base Pairing

  16. DNA Replication Hypotheses

  17. Meselson-Stahl Experiment (1957)

  18. Semiconservative DNA Replication

  19. Semiconservative DNA Replication

  20. Origins of Replication

  21. 3’ OH Nucleotide Incorporation Pyrophosphate hydrolysis powers nucleotide addition

  22. Lagging & Leading Strands Both daughter strands are laid down in the 5’ to 3’ direction ~100-2000 bases long, depending on species

  23. Leading vs. Lagging Strands

  24. Solves DNA polymerase requirement for 3’ OH Lagging-Strand Syn. (1/2)

  25. Lagging-Strand Syn. (2/2)

  26. Replication Fork Components Yes, difficult to read, but it is in your text!

  27. DNA Replication Enzymes

  28. Replication Fork Topoisomerase acts here

  29. Proofreading “During DNA replication, DNA polymerases proofread each nucleotide against its template as soon as it is added to the growing strand. Upon finding an incorrectly paired nucleotide, the polyerase removes the nucleotide and then resumes synthesis. (This action is similar to fixing a typing error by using the ‘delete’ key and then entering the correct letter.)” p. 305, Campbell & Reece (2005)

  30. Excision Repair

  31. The Problem of Ends Erosion of ends

  32. A Solution: Telomeres Telomere are sequences found on the ends of Eukaryotic DNA that are added on by an enzyme called telomerase Telomeres erode so that genes don’t have to!

  33. Central Dogma Preview

  34. Central Dogma Preview

  35. The End

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