1. Today: Notes Quiz 12-1 Lecture on History Race to the Double Helix

2. DNA HISTORY !

3. Homework up till Winter Break! Wednesday: Read/notes Chapter 12 Section 1 Thursday: Twist of Fate Article w/ Questions p. 49-52 Friday/Weekend: Twist of Fate Article w/ Questions p. 53-56 Monday: Twist of Fate Article w/ Questions p. 57-58 Tuesday: DNA Coloring Next Friday: DNA History Test!

4. How did scientists determine which molecule carries genetic information from parent to offspring and gives us our traits? PROTEIN VS DNA

5. Griffith’s Contribution 1928: Griffith discovered that one bacteria can transfer it’s genetic information to another bacteria. Transformation! How did he do it…by killing a lot of mice  But…we still didn’t know what molecule controlled the genetic information. FYI: You will do this in lab second semester…transformation, not mouse killing.

6. What does bacteria really look like when it is grown in a lab?

7. When he killed the “bad” bacteria, a few survived and passed those “survivor” traits to the “good” bacteria along with the rest of it’s genetic information.

8. Avery’s Contribution 1944: Avery repeated Griffith’s experiment but he destroyed all proteins first. Transformation still occurred proving that the “transforming” material was DNA. How did he do it…by killing more mice 

9. Hershey & Chase’s Contribution 1952: Tagged a bacteriophage (virus that invades bacteria) with radioactive markers on the protein molecules and the DNA. Observed that when the virus injects it’s genetic information into the bacteria, that molecule is actually DNA and not a protein. How did he do it…not by killing mice

11. Now that multiple experiments have proven DNA to be the genetic molecule, the race was on to discover DNA’s structure and function.

12. Franklin’s Contribution 1952: Franklin uses x-ray diffraction technology to gain clues to DNA structure. Helical?Double Helix?Triple Helix? How did she do it…by personally absorbing many x-rays 

13. Chargaff’s Contribution 1952: Chargaff studies the % of each nucleotide in a DNA sequence for multiple organisms. Discovers that % adenine = % thymine % cytosine = % guanine How did he do it…extracting DNA from a large variety of organisms.

15. Watson & Crick’s Contribution 1952: Built a three dimensional model of DNA showing the double helical structure. Published their findings in Nature magazine sharing with the world the structure of DNA. How did they do it…by applying the experimental results from many scientists and applying this to model building.

16. Side Note…Maurice Wilkins Franklin worked with Maurice Wilkins who was also a leading x-ray diffraction scientist. Wilkins helped Watson & Crick interpret Franklin’s images so they could build their double helical model.

17. ScientistPictureLocationYearContribution GriffithEngland1923 Genetic information can be transferred from one bacteria to another Avery New York, US 1944 DNA is the genetic material transferred in Griffith’s experiment. Hershey- Chase New York, US 1952 Used bacteriophage to prove DNA is the molecule containing genetic information. Chargaff New York, US 1950%A = %T; %G = %C FranklinEngland1952 X-Ray images suggest double helix. Watson- Crick England1952 Built model proving DNA’s double helical structure. WilkinsEngland1952 Helped Watson and Crick interpret Franklin’s images.