1 / 16

MOLECULAR GENETICS

MOLECULAR GENETICS . UNIT 3!. Reflect on your Learning. Answer questions 1,2,and 3 on the bottom of page 204. . History of DNA. Before the 20 th Century: It was believed that proteins were the hereditary material (because they are so prevalent in the cell) Friedrich Miescher 1869

alia
Download Presentation

MOLECULAR GENETICS

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. MOLECULAR GENETICS UNIT 3!

  2. Reflect on your Learning... • Answer questions 1,2,and 3 on the bottom of page 204.

  3. History of DNA Before the 20th Century: It was believed that proteins were the hereditary material (because they are so prevalent in the cell) Friedrich Miescher • 1869 • Used pus cells to investigate the material inside the nucleus • Called this substance nuclein.  did not behave like proteins. • Did not know this was the hereditary material.

  4. Hammerling • 1930s • Used Acetabularia, a one-celled green algae to investigate WHERE hereditary information was stored in the cell. • Reaches 5 cm in length: great to work with. • Three distinct parts: • Foot (contains the nucleus) • Stalk • cap

  5. The hereditary information must be in the foot (and possibly the nucleus)

  6. He furthered his experiments: • Two species of Acetabularia: • A. Mediterranea: disk-shaped cap • A. Crenulata: branched, flowerlike cap. • Grafted stalk of A.c onto foot of A.m. • Subsequent cap was an intermediate between the two species: because substances that determined cap type were still in the stalk. • Excised the cap and found that the new cap formed was A. m: substances in the transplant were used up  under the control of the new nucleus. • Concluded that YES, the hereditary material is in the nucleus.

  7. The Transforming Principle • Nucleus was known to be the site of hereditary information. • Chromosomes consist of both DNA and proteins. • Which one was responsible for inheritance?

  8. Alfred D. Hershey and Martha Chase • Not until 1952 that DNA accepted as hereditary material. • Conducted experiments using a virus, bacteriophage T2: __________________. (Bacteriophages are commonly called phages) • Two components • DNA • Protein coat.

  9. How viruses work: • Attach to membrane • Inject hereditary information (PROTEIN COATS REMAIN OUTSIDE OF THE CELL) • DNA of phage takes over cell mechanics • Cell makes components (proteins and nucleic acids) of the virus • Cell assembles components into new viruses • New viruses burst out of the cell, resulting in host cell’s death • New viruses can then infect other cells.

  10. Key aspects: • Proteins contain sulfurbut no phosphorous • DNA contains phosphorus and no sulfur • Hershey and Chase tracked the location of DNA and proteins throughout infection. • Tagged some viral proteins with an isotope of sulfur, 35S • Tagged some viral DNA with an isotope of phosphorus, 32P. • Both 35S and 32P are radioisotopes: emit radiation as they decay: can be tracked. • Both types of tagged T2s were allowed to infect bacterial cells. • Cells put in blender and centrifuged to isolate bacteria parts (pellet) and viral parts (liquid)

  11. Results? • Bacterial cells infected by 35S – containing viruses did NOT contain any radioactivity. • Bacterial cells infected by 32P – containing viruses DID contain radioactivity. • THEREFORE, PHOSPHORUS-RICH DNA WAS INJECTED INTO THE BACTERIAL CELL. • This must be the genetic information.

  12. Seatwork/Homework Page 209, #2, 3, 4, 5.

More Related