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Unit 3 Nucleic Acids

Unit 3 Nucleic Acids. Nucleic Acid-. A large complex organic molecule that stores and transmits genetic information DNA & RNA. Evidence. Supporting the role of DNA in living things. Transformation-. To change from one form to another. Transformation Experiment. S. Pneumoniae Bacteria

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Unit 3 Nucleic Acids

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  1. Unit 3Nucleic Acids

  2. Nucleic Acid- • A large complex organic molecule that stores and transmits genetic information • DNA & RNA

  3. Evidence • Supporting the role of DNA in living things

  4. Transformation- • To change from one form to another

  5. Transformation Experiment • S. Pneumoniae Bacteria • R strain- harmless • S strain- virulent (disease causing) • Mice

  6. Experiment 1 with Bacteria (p194) • R cells  injected  mice live

  7. Experiment 2 with Bacteria (p194) • S cells  injected  mice die

  8. Experiment 3 with Bacteria (p194) • Heat killed S cells  injected  mice live

  9. R cells + heat killed S cells  injected  Experiment 4 with Bacteria (p194)

  10. Question 1. Based on results of Exp 1, 2, & 3, what do you think happened in Exp 4? Answer- Mice Live 2. Could cells injected in Exp 4 cause pneumonia before they were injected? Answer- No

  11. Experiment 4 with Bacteria (p194) • R cells + heat killed S cells  injected  mice die

  12. Questions • 3. How did the bacteria that resulted in Exp 4 differ from ones injected? • Answer- Living S cell present. • Read through the Extension • 4. Was this difference only in their structure? • Answer- No, since trait is passed on, the genetic message must also have been changed.

  13. Questions • 5. Give an explanation as to what happened in Exp 4. • Answer- DNA from heat killed S cells used in R cells & changes them into living virulent S cells

  14. Transforming Factor- • Factor that causes the transformation- • Avery tested in 1940’s, determined it was DNA

  15. Bacteriophage (p. 195) • A virus that infects a bacteria • Consists of a protein coat and DNA • Problem- Is it the protein coat or DNA that is hereditary material a virus transfers to a bacterium?

  16. Hershey-Chase Experiment (p 195 ) • 1. Used radioactive sulfur to tag protein coat. • 2. Used radioactive phosphorous to tag the DNA. • 3. Used blender to separate the virus coat from bacteria. • Detected radioactive phosphorous in the bacteria. Concluded DNA enters bacteria.

  17. All Images- Clip Art

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