1. DNA: a history DNA model Double helix nebula

2. Griffith experiment: 1928 A heat-killed lethal strain of bacteria was added to a non-lethal strain. The non-lethal strain was transformed into a lethal one. 1944: Avery: DNA is the molecule involved. DNA stores and transmits genetic information from one generation to the next non-lethal lethal heat-killed lethal transformed

3. Hershey-Chase experiment 1952 Added radioactive markers to the proteins and DNA of viruses Only the tracers attached to DNA entered the bacteria. The genetic material of viruses is DNA

4. Components of DNA A long molecule made of chains of nucleotides: 5-C sugar Phosphate Nitrogen-containing bases One nucleotide group

5. Ribose sugar Phosphate 4 Nitrogen bases Adenine, Thymine, Cytosine Guanine

6. DNA structure Chargaff’s rules: the amount of Adenine = Thymine Cytosine = Guanine 1953: Watson and Crick discover the double helix structure of DNA, where 2 strands wind around each other Franklin’s X-ray diffraction of DNA Watson and Crick’s original DNA model

7. A twisted ladder Rungs: Bases held by H bonds connect at the center. Sides: Sugar and Phosphate Bases attach to the ribose sugars

8. Base pairing Hydrogen bonds form between A and T and between C and G. A fits with T G fits with C This explains Chargaff’s rule

9. Copyright Pearson Prentice Hall The Components and Structure of DNA

10. Hydrogen bonds form at the center of the rungs, between the N base molecules

11. DNA has been found in every organism on earth