2. CHAPTER 9 SECTIONS 2 & 3

3. Stores and passes on genetic information from one generation to another. Sugar: deoxyribose DNA Deoxyribonucleic acid

4. DNA STRUCTURE Shaped like a spiral staircase, or twisted ladder. Double Helix

5. DNA – Scientists who mapped its structure Chargaff’s 1949 Observations: The amount of adenine always equaled the amount of thymine (A = T) The amount of cytosine always equaled the amount of guanine (C = G)

6. DNA – Scientists who mapped its structure Wilkins & Franklin’s Photographs Using x-ray diffraction, in 1952 Developed high-quality photographs of strands of DNA Suggested that DNA was a tightly coiled helix with 2 or 3 strands of nucleotides

7. DNA – Scientists who mapped its structure Watson & Crick’s 3-D DNA model in 1953 “Watson & Crick, took a stick and built the DNA model.”

8. DNA STRUCTURE The outer parts of the ladder are made of: a sugar (deoxyribose) + a phosphate.

9. DNA STRUCTURE The rungs (steps) of the ladder are pairs of nitrogen bases… …held together with weak hydrogen bonds.

10. DNA STRUCTURE 1.ADENINE = A 2.GUANINE = G 3.CYTOSINE = C 4.THYMINE = T They are represented by their capital letter.

11. Base Pair Bonding Rules A DENINE WITH T HYMINE (“Stick” Family) T & A C YTOSINE WITH G UANINE (“Curve” Family) C & G

12. DNA STRUCTURE QUESTION ? CAN T JOIN WITH A AND G JOIN WITH C YES NO

13. CORRECT MOVE ON

14. SORRY REVIEW MORE

15. DNA STRUCTURE ACTCATGGTCATG TGAGTACCAGTAC This is an example of a genetic code that may be found in your body.

16. DNA STRUCTURE The combinations of the nitrogen bases is the code that produces the genes for a particular trait.

17. DNA STRUCTURE Because there can be so many different combinations of the bases, the code can be limitless

18. DNA STRUCTURE EXAMPLE: ATCGTCAGG May be for hair color. BUT ATCGTCAGC May be for eye color

19. Stop Begin DNA Model

20. DNA Replication Replication: to make anReplication: to make an identical copy of identical copy of Occurs during the “S” phase of the cell cycle. (Just before mitosis)

21. DNA Replication Also known as: Semi-Conservative Replication – –semi: half – –Conserve: to save or reuse – –Replicate: to copy exactly

22. Semi-conservative Replication To reuse half of the original DNA strand to make an exact copyTo reuse half of the original DNA strand to make an exact copy

23. DNA REPLICATION 1.DNA Ladder Splits (unzips) enzyme DNA helicase

24. 2.Free floating nitrogen bases begin to pair on each strand Attached by the enzyme DNA polymerase (the glue) Semi-conservative Replication

25. Semi-conservative Replication (attaching bases)

26. 3. Two new identical DNA chains are formed Semi-conservative Replication

27. DNA REPLICATION

28. FYI Each human chromosome is replicated in about 100 sections that are 100,000 nucleotides long. An entire human chromosome can be replicated in about 8 hours!

29. http://highered.mcgraw- hill.com/sites/0072437316/student_view0/chapter1 4/animations.html# DNA Animation View “DNA Replication Fork”