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The History and Structure of DNA (Chapter 13)

The History and Structure of DNA (Chapter 13). DNA :___________________. _________ are made up of small segments on a chromosome (made of deoxyribonucleic acid or “DNA ”) DNA is the primary material that causes recognizable, inheritable characteristics in related groups of organisms.

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The History and Structure of DNA (Chapter 13)

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  1. The History and Structure of DNA(Chapter 13)

  2. DNA:___________________ • _________ are made up of small segments on a chromosome (made of deoxyribonucleic acid or “DNA”) • DNA is the primary material that causes recognizable, inheritable characteristics in related groups of organisms.

  3. Searching for the Genetic Material 3 major _______________________ ________________________________________________________

  4. 1. - 1928 • Worked with 2 types of bacteria in mice (S bacteria & R bacteria) • Discovered “transformation” – the transfer of genetic material in the form of DNA fragments from one cell to another.

  5. Conclusion of Griffith’s Experiment: • Something is present in the Smooth bacteria that is capable of transforming the Rough into Smooth • This “mystery substance” is _________ _________________________________ Hmmm…what could this mystery substance be?

  6. 2. Avery, McCarty & MacLeod • 1944—Wanted to determine whether the transforming agent in Griffith’s experiments was a_________________ _________________________________ • Used enzymes to destroy each of these molecules in the Smooth (disease-causing) bacteria.

  7. Avery, McCarty & MacLeod’s Experiment, Step by Step: • Step 1: Using enzymes, they took the heat-killed smooth bacteria and removed the carbohydrates. After adding this to the Live Rough bacteria, they injected mice. • The mice died of pneumonia. This means the Live Rough still turned into Smooth.

  8. Avery, McCarty & MacLeod’s Experiment, Step by Step: • Step 2: This time, they used enzymes to destroy the lipids in the heat-killed smooth. After adding it to the Live Rough, they injected mice. • The mice died of pneumonia. This means the Live Rough still turned into Smooth, even without the lipids.

  9. Avery, McCarty & MacLeod’s Experiment, Step by Step: • Step 3: This time, they used enzymes to destroy the proteins in the heat-killed smooth. After adding it to the Live Rough, they injected mice. • The mice died of pneumonia. This means the Live Rough still turned into Smooth, even without the proteins.

  10. Avery, McCarty & MacLeod’s Experiment, Step by Step: • Step 4: This time, they used enzymes to destroy the DNA in the heat-killed smooth. After adding it to the Live Rough, they injected mice. • The mice lived! This means the Live Rough stayed Rough! Without the DNA from the smooth, the Rough did not turn into smooth.

  11. Conclusion of Avery’s Experiment: • ________________________________ _________________________________ Were their findings accepted by the scientific community?

  12. 3. Alfred Hershey & Martha Chase - 1952 • Worked with bacteriophages (infectious viruses) made up of proteins and DNA. • Found that DNA is the hereditary material in viruses.

  13. Life Cycle of a Virus Thanks to the Hershey-Chase Experiment, we now know what part of the virus is injected into the cell.

  14. Hershey-Chase Experiment:

  15. Conclusion of the Hershey/Chase Experiment: • ________________________________ _________________________________

  16. The Race is On…… • In the 1950s, we knew genes were made of DNA but knew nothing about its ___________. • Scientists around the world were actively searching for more information about DNA

  17. ___________________________ • Received his doctoral degree at age 22 in Zoology, with an emphasis on genetics. He also did post-doctoral research in biochemistry. • Francis Crick, 36, a physicist working at Cambridge University in England James Watson Francis Crick

  18. James Watson & Francis Crick • ____________________________________ _____________________________________ • The chains are twisted around a central axis and are held together by weak ___________________.

  19. How did Watson & Crick determine this structure?(3 contributions) 1. In 1949, Erwin Chargaff found that there was always the same percent of ____________________and the same percent of _______________________. This is known as ___________________

  20. 2. In 1952, Rosalind Franklin & Maurice Wilkins developed high quality ______ ____________________ Images resembled a tightly coiled helix of 2 chains.

  21. 3. In 1953, Watson & Crick used the findings of _____________________to create a 3-D _______________.

  22. DNA Nucleotide Subunits:phosphate/sugar backbone with nucleotide bases

  23. The 4 Nitrogen Bases:

  24. Nitrogenous Bases • _________– Have 2 rings of carbon & nitrogen atoms per base. A – ___________ G – ___________ • _____________– Have 1 ring of C & N atom per base T – ____________ C – ____________

  25. Base- Pairing Rules • A purine on one strand of DNA is always paired with a pyrimidine on the other • _____________ • _____________

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