1. Chapter 13: DNA

2. I. Mystery of DNA Structure A.Griffith (1920s): Injected mice with deadly bacteria (rough colony) and they die. Inject mice with smooth bacteria and they live. Inject mice with heat-killed rough and they live. Mix heat-killed rough with healthy smooth, mice die. Conclusion: Transforming factor smaller than cell.

3. I. Mystery of DNA Structure B. Hershey/Chase (1950s) Radiolabeled proteins and DNA. Found viruses injected radiolabeled DNA, but no proteins. Conclusion: DNA is transforming factor.

4. Figure 16.2a The Hershey-Chase experiment: phages

5. Fig. 13.5, p. 217 virus particle labeled with 35 S virus particle labeled with 32 P bacterial cell (cutaway view) label outside cell label inside cell

6. I. Mystery of DNA Structure C. Chargaff (1950s): Worked with DNA and found that the amount of adenine (A) equaled the amount of thymine (T) while the amount of cytosine (C ) equaled the amount of guanine (G). Conclusion: Chargaff’s base-pairing rule.

7. I. Mystery of DNA Structure D. Franklin/Wilkins (1953): X-ray crystalography They froze DNA and ran x-rays through resulting crystal. Conclusion: DNA tightly-wound helix (at least they provided the evidence for this conclusion).

8. Figure 16.4 Rosalind Franklin and her X-ray diffraction photo of DNA

9. I. Mystery of DNA Structure E.Watson & Crick (1953): Assemble all evidence and correctly interpret data to create double helix. Conclusion: Current model of DNA (and Noble prize and fame and glory and chicks)

10. II. Model of DNA A.Nucleotide: Basic building block of DNA. 1 phosphate group, 1 deoxyribose sugar, 1 nitrogenous base.

11. II. Model of DNA A. Nucleotide: 1.Sugar (Deoxyribose): Each carbon is numbered sequentially.

12. Fig. 13.7, p. 219 2-nanometer diameter, overall distance between each pair of bases = 0.34 nanometer each full twist of the DNA double helix = 3.4 nanometers

13. A.Nucleotide 2. Phosphate: Negative yet next to each other along DNA backbone, resulting in twisting.

14. II. Model of DNA A. Nucleotide: 3. Nitrogenous Bases: Adenine and Guanine are Purines (double ring structures) Cytosine and Thymine are Pyrimadines (sing ring structures)

15. Fig. 13.6, p. 218 phosphate group sugar (ribose) ADENINE (A) base with a double-ring structure THYMINE (T) base with a single-ring structure CYTOSINE (C) base with a single-ring structure GUANINE (G) base with a double-ring structure

16. II. Model of DNA B. Bonds within DNA Molecule 1. Phosphate to Sugar: Covalent (note which carbon in sugar is attached to which phosphate).

17. II. Model of DNA B. Bonds within DNA Molecule 2. Sugar to Nitrogenous Base: Covalent. 3. N-base to N-base: Hydrogen Bonds.

18. II. Model of DNA C. Complete molecule is ‘antiparallel’ (one side runs 3’ to 5’, other side runs upside down, or 5’ to 3’)

19. wxC in-text, p. 219 For each, 1. How many base pairs? 2. How many nucleotides? 3. How many sugars? 4. Circle a hydrogen bond.

20. III. DNA Replication A.Replication: Occurs in the nucleus; process of DNA creating an exact replica of original strand.

21. III. DNA Replication B. Semi-Conservative Nature of Replication The two daughter strands are half new and half original (order and molecules of parent strand are conserved ). Each half of original strand becomes a template for each new DNA molecule. The new strand is half old, half new.

22. III. DNA Replication C. Steps of Replication: 1. DNA uncoils and unzips (done by enzyme DNA helicase). 2. New nucleotides are added to exposed strand and added by DNA polymerase enzyme. 3. DNA ligase fills in gaps in new DNA strands.

23. III. DNA Replication D. Okazawi Segements: DNA is read from 3’ to 5’. 1. Leading strand reads 3’ to 5’ as DNA is unzipped. 2. Lag strand would have to wait for entire strand of DNA to unzip to begin; rather it builds short segments, known as Okazawi segments (later ‘stitched’ together with DNA ligase).

24. Note 3’ to 5’ direction:

25. Figure 16.13 Synthesis of leading and lagging strands during DNA replication

26. Label Middle image 3’ to 5’

27. Okazaki Segment Illustrated

28. III. DNA Replication E. Replication Fork/Bubble: As DNA unzips, it replication begins immediately. Replication simultanelously occurs at many sites along a strand of DNA.

29. Figure 16.10 Origins of replication in eukaryotes