1. DNA  History  Structure  Replication

2. History of DNA Scientists thought protein was the heredity material Several Scientists disproved this and proved it was DNA:

3. Griffith Worked with virulent S and nonvirulent R strain of pneumococcus bacteria Made the harmless R strain transform into S strain when it took in DNA from the killed S strain.

4. Hershey & Chase Worked with radioactively traced bacteriophages (viruses that attack bacteria). Further proof that DNA was the cell’s genetic material. Radioactive 32 P was injected into bacteria!

5. Chargaff Developed the base pairing rule by comparing the amounts of A, T, C, G in the cell. Nucleotide pairing: – Adenine  Thymine – Guanine  Cytosine

6. Franklin Took x-ray photographs of DNA Determined double-helix structure

7. Watson & Crick Watson and Crick used Franklin’s x-rays, Chargraff’s rule and developed their model of the DNA molecule (for which they won a Nobel Prize).

8. Structure of DNA

9. Shape of DNA Double stranded, twisted helix, called a double helix Shape similar to a twisted ladder

10. Nucleotide Monomers DNA Nucleotide is the basic unit (monomer) Made of: Sugar – Deoxyribose Phosphate group (PO 4 ) Base – A T C G (Adenine, Thymine, Cytosine, Guanine)

11. DNA Nucleotide ( glue picture provided in NB) N O O=P-O OPhosphate Group Group Nitrogenous base (A, G, C, or T) (A, G, C, or T) CH2 O C1C1 C4C4 C3C3 C2C2 5 Sugar Sugar(deoxyribose)

12. Polymer Structure Sides made of phosphate group and deoxyribose sugar Center (rungs) made of nitrogen bases bonded by hydrogen bonds (A = T and C = G)

13. Direction of Nucleotides Each carbon in the sugar is given a number 1’ – 5’ Sides are antiparallel – one side goes 5’ to 3’ and the other 3’ to 5’ This determines the direction that it is “read” by enzymes

14. DNA Structure (glue picture provided in NB) P P P O O O 1 2 3 4 5 5 3 3 5 P P P O O O 1 2 3 4 5 5 3 5 3 G C TA

15. Location of DNA DNA is a large (macro) molecule, and stays in the nucleus

16. DNA Replication

17. S Phase of Cell Cycle DNA must be copied before the cell can divide Occurs during the synthesis (S) part of cell cycle (before mitosis). Mitosis -prophase -metaphase -anaphase -telophase G1G1 G2G2 S phase interphase

18. Helicase enzyme DNA unwinds and unzips with help of DNA helicases These enzymes break the hydrogen bonds between base pairs. This point is called the replication fork. ReplicationFork Parental DNA Molecule 3’ 5’ 3’ 5’

19. Polymerase Enzyme DNA polymerase moves in new nucleotides Can only add to 3’ end of nucleotide Follows the base-pairing rule Two identical DNA strands are formed RNAPrimer DNA Polymerase Nucleotide 5’ 3’ Direction of Replication

20. Proofreading enzymes Other enzymes “proofread” the replicated strand looking for errors (mutations). Incorrect nucleotides are removed and replaced