1 / 11

Unveiling Genetic Mysteries: DNA Code Revelation

Explore the historic experiments of Griffith, Avery, and Hershey-Chase that led to the discovery of DNA as the molecule of heredity. Learn how genes are stored on chromosomes and the language of interpreting the molecular code.

eyoungman
Download Presentation

Unveiling Genetic Mysteries: DNA Code Revelation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 8:DNA and RNA Section 8-1: Discovering DNA

  2. The Language of Genes • In order to understand how genes are stored on chromosomes, biologists had to learn the molecule of heredity and the language to interpret the molecular code.

  3. Griffith and Transformation • Frederick Griffith (Britain, 1928) • Studying causes of pneumonia, isolated two types of bacteria from victims – “smooth” and “rough” • Injected mice with both types of bacteria – those injected with smooth bacteria developed pneumonia

  4. Griffith and Transformation • First major experiment – Griffith heated a sample of smooth bacteria, injected it into mice • Result = no pneumonia, concluded heat killed all bacteria

  5. Griffith and Transformation • Second experiment – mixed heat-killed smooth bacteria with harmless rough bacteria • Result = mice developed pneumonia and died • Samples taken from mice showed live, smooth bacteria

  6. Griffith and Transformation • Conclusion – Some molecule or group of molecules had changed harmless rough bacteria into deadly smooth bacteria. • Process called transformation

  7. Avery and DNA • Oswald Avery (Canada, 1944) • Said key to finding molecule of heredity was studying transformation • Hypothesized genes had been transferred in Griffith’s experiments • Conducted experiments in which heat-killed bacteria were treated with enzymes to destroy macromolecules

  8. Avery and DNA • In all cases, transformation still occurred EXCEPT when DNA was destroyed • Conclusion – Genes are made of DNA

  9. Hershey-Chase Experiment • Alfred Hershey and Martha Chase (USA, 1952) • Studied bacteriophages, type of virus that infects bacteria • Attach to outside of bacterium, inject something into bacterium that allow it to make more viruses • Viruses only contain DNA and protein – which ones contains genes?

  10. Hershey-Chase Experiment • Used radioactive isotopes to label viral DNA and protein • Phosphorus-32 used to label DNA, sulfur-35 used to label protein

  11. Hershey-Chase Experiment • Bacteria infected and analyzed - only phosphorus-32 found in infected bacteria • Conclusion – Genetic material of bacteriophage is DNA, not protein.

More Related