1. Section 2 DNA Structure  DNA Double Helix  Watson and Crick created a model of the DNA.  Illustration:

2. DNA  DNA: Contains the hereditary characteristics of an organism.  Function of DNA: Store and transmit genetic material.

3. DNA  Deoxyribonucleic acid  It’s a nucleic acid made up of two long chains called nucleotides.  Nucleotides: consist of three parts:  A five carbon sugar  A phosphate group  A nitrogen base

4. Nucleotides  The five carbon sugar in a DNA nucleotide is called deoxyribose.  The phosphate group consists of a phosphate atom bonded to four oxygen(O) atoms.  The nitrogen base contains nitrogen (N) atoms and carbon(C) atoms.

5. DNA double Helix  Two chains held together by hydrogen bonds. Each full turn of the DNA helix has 10 nucleotide pairs, made up of two strands of nucleotides that twist into a shape that resembles a spiral staircase.

6. 4 Nitrogen bases  Thymine(T)  Cytosine(C)  Adenine(A)  Guanine(G)

7. Nitrogen Bases  Purines: nitrogen bases that have double rings of carbon and nitrogen.  Example: Adenine and Guanine  Pyrimidines: Nitrogen bases that have a single ring of carbon and nitrogen atom.  Example: Cytosine and Thymine

8. Bases Pairing ATTCG  TAAGC  Base pairing rules:  cytosine pairs with guanine.  Adenine pairs with thymine.  Cells--> Nucleus --> Chromosomes --> DNA  -->DNA double helix.

9. Nucleotide

12. BASES