1. The Structure of DNA The Double Helix

2. DNA = Deoxyribonucleic acid DNA is made up of small sub units called Nucleotides A Nucleotide Has 3 major parts -Sugar (Deoxyribose) -Phosphate Group -Nitrogen Base

3. Phosphate

4. Sugar = Deoxyribose

5. Nitrogen Base Adenine Guanine Thymine Cytosine Uracil is used only in RNA

6. A single strand of DNA looks a little like this:

7. Two Strands of DNA are held together by hydrogen bonds

8. The double helix: refers to two stands of DNA held together by hydrogen bonds between complementary Nitrogen bases.

9. Nitrogen bases fit together like puzzle pieces Cytosine bonds to Guanine Adenine bonds to Thymine These “bases” make the steps on a ladder The Phosphate and sugar Makes the “Backbone” A closer look at a bacteria Chromosome

10. When DNA is not being used it is tightly coiled around proteins called “Histones” to form a Chromosome Chromosome Supercoils Coils Nucleosome Histones DNA double helix

11. How did they discover the structure? Rosalind Franklind took this X-ray Diffraction Picture James Watson and Francis Crick used the photo as they were developing their model… They never gave her credit for her work and she died of ovarian cancer likely due to exposure to the X-rays of her work

12. Images From Prentice Hall Presentation Pro CH 12 http://en.wikipedia.org/wiki/Photo_51 http://en.wikipedia.org/wiki/Rosalind_Frank linhttp://en.wikipedia.org/wiki/Rosalind_Frank lin http://en.wikipedia.org/wiki/DNA