1. DNA

2. How was DNA discovered? There were 3 major experiments that led to the discovery of DNA as the genetic material. –Griffiths Transformations –Avery –The Hershey-Chase Experiment

3. Griffiths Griffith’s injected bacteria into mice. He showed that something in the smooth bacteria TRANSFORMED the non-deadly rough.

4. Avery and DNA Avery wanted to figure out what exactly transferred from the smooth strain to the rough. –One at a time he used enzymes to destroy the: Proteins Lipids Carbohydrates RNA Still the smooth bacteria tranferred something All that was left was the DNA!!!!

5. Hershey and Chase Studied viruses that infect bacteria – called bacteriophage. Bacteriophages are simple: just DNA or RNA and a protein coat. The labeled the DNA OR protein coat with a a radioactive marker. What they found was the DNA entered the cells, not the proteins.

6. Only the DNA entered the cell Therefore DNA must be the genetic material

7. DNA Deoxyribonucleic Acid Made up of units called nucleotides –Each nucleotide has 3 parts: A) 5-Carbon sugar B) Phosphate group C) nitrogenous base

8. Nuclotides – differ in the Nitrogen Base! Nucleotides belong to 1 of 2 groups: Purines: Have 2 rings in their structure –Adenine –Guanine Pyrimidines: 1 ring –Cytosine –Thymine

9. Structure of DNA These 4 nucleotides are linked in various ways and order – creating DNA. There are 2 strands of DNA The sugar and the phosphate make up the backbone of the DNA. One nucleotide from each strand come bond together to form what looks like ladder rungs.

10. Chargaff Chargaff’s Rules –Erwin Chargaff showed that in most samples of DNA the Percentages of Cytosine and Guanine were equal. –Likewise, the Adenine and Thymine Percentages were also very close.

11. Percentages of Bases in Organisms OrganismATCG Human30.929.419.919.8 Chicken28.829.220.521.5 Yeast31.332.918.717.1 E. coli24.723.626.025.7

12. Shape of DNA In the 1950’s Rosalind Franklin looked at the shape of DNA. Used technique called X-Ray Diffraction Her work showed that the strands of DNA wrap around each other  called a Double Helix Watson and Crick used Franklin’s X-Ray diffraction to build a model of DNA

14. DNA DNA is a long chain of repeating nucleotides. DNA has 2 strands to it The phosphate group of one nucleotide is bonded to a sugar group of the next nucleotide. The nitrogenous bases of one strand extends out and bonds with a complementary nitrogenous base on the other DNA strand.