1. STRUCTURE OF DNA

2. SUGAR
Deoxyribose

3. PHOSPHATE

4. NITROGENOUS BASES Purines- 2 organic rings/ Adenine & Guanine
Pyrimadines- 1 organic ring/ Thymine & Cytosine

5. CONSTRUCTION

6. BONDS Covalent: between sugar and phosphate Hydrogen: between bases
2 bonds between A and T
3 bonds between G and C

7. ANTI-PARALLEL ARRANGEMENT
Sugar-phosphate backbones run in opposite directions
3’ and 5’ Ends- note the carbon # of the sugar where it joins to the phosphate:
3’ end joins to phosphate at carbon 3 on sugar
5’ end joins to phosphate at carbon 5 on the sugar

8. ANTIPARALLEL ARRANGEMENT

9. ENZYMES FOR REPLICATION
Helicase- unzips hydrogen bonds between bases

10. ENZYMES FOR REPLICATION
Primase- joins RNA nucleotides to make the primer- later replaced by DNA nucleotides using DNA polymerase- only one primer needed to initiate replication
DNA polymerase- joins nucleotides to sugar- (50 nucleotides per second in human cells)

11. ENZYMES

12. OKAZAKI FRAGMENTS Short fragments of DNA added to the lagging strand-
nucleotides long in eukaryotes
Joined together by DNA ligase to make complete
strand