1. DNA STRUCTURE AND REPLICATION CHAPTER 11.1-11.3

2. What is DNA? Hereditary material present in all living cells Composed of monomers called nucleotides Is part of the chromosomes What are chromosomes composed of? Before ~ 1940 people did not really know what the genetic material was

3. A history of DNA Friedrich Miescher, 1871 isolated nuclei from pus and identified nuclein later called nucleic acid. Archibald Garrod, 1902 linked inheritance of “inborn errors of metabolism” with the lack of particular enzyme proteins. Shows that something must be passed on from parent to offspring

4. WHICH IS MORE LIKELY TO BE GENETIC MATERIAL? ProteinDNA

5. FREDERICK GRIFFITH’S EXPERIMENTS in 1928 Worked with two types of pneumonia causing bacteria: S-strain covered by a capsule and causes pneumonia R-strain had no capsule and was not dangerous Mice that were injected with the bacteria to see if they contracted pneumonia

6. Injection Bacterial colonies Rough nonvirulent (strain R) Results Mouse healthy Smooth virulent (strain S) Mouse dies Heat-killed smooth virulent (strain S) Live strain S bacteria in blood sample from dead mouse Mouse dies Mouse healthy + Rough nonvirulent (strain R) Heat-killed smooth virulent (strain S) Griffith’s experiment identifying the “transforming principle”

7. FREDERICK GRIFFITH’S RESULTS R bacteria (safe) mixed with heat-killed S bacteria (capsule still present) killed the mouse Griffith’s discovery: TRANSFORMATION, Something (presumably the hereditary material) from the heat killed S bacteria transferred to the safe R bacteria and changed its genetic composition to give pneumonia

8. OSWALD AVERY’S EXPERIMENT Repeated Griffith’s experiments, utilizing enzymes to destroy DNA, RNA, and protein, respectively Missing protein? Protease to kill all proteins Transformation still occurs Missing DNA? DNAse to kill all DNA - No transformation

9. What is the “transforming principl e”? Conclusion: DNA is the transforming principle allowing R bacteria to make a smooth coat and allow infection

10. HERSHEY-CHASE EXPERIMENT in 1953 When a virus infects a bacteria, it produces more viral particles which are identical to the parent virus. So …. STEP 1: Viral proteins and DNA “marked” with two different radioactive elements S 35 for proteins – coats radioactive P 32 for DNA – genetic material radioactive

11. HERSHEY-CHASE EXPERIMENT STEP 2: Viruses “infect” bacteria STEP 3: Radioactive elements can be detected by machines Conclusion: Examine infected bacteria Found radioactive DNA inside the bacteria Radioactive proteins – outside the bacteria

12. Nucleotide of DNA

13. What does the DNA look like? Activity usi ng puzzle pieces

14. DNA bases pair via hydrogen bonds Erwin Chargaff observed: # of adenine = # of thymine # of guanine = # of cytosine Complementary bases pair: A and T pair C and G pair

15. UNRAVELING DNA Pauling (Caltech) pioneered X-ray crystallography Rosalind Franklin’s X-ray images taken by Maurice Wilkins Franklin (died in 1958 of cancer) did not get the Nobel Prize in 1962 Conclusion: Repeating double helix structure

16. WATSON AND CRICK: “THE DOUBLE HELIX”

17. DNA Structure 1.DNA made up of two twisted strands 2.Adenine pairs w/Thymine 3.Cytosine pairs w/Guanine 4.Two strands held together by weak hydrogen bonds 5.The sugar and phosphate make the backbone (or sides of ladder)of the molecule 6.Nitrogen bases make the middle or (rungs of ladder)

18. WHAT IS THE COMPLEMENTARY STRAND? A C G C C A G T A

19. WHAT IS THE COMPLEMENTARY STRAND? A C G C C A G T A T G C G G T C A T

20. What is the role of the genetic material and what is a gene? The genetics material has to be able to carry out two jobs Faithfully duplicate itself to transfer the same genetic information to daughter cells during cell division Express itself and make proteins for the cell to carry out it duties A gene is a segment of the DNA containing an unique sequence of bases that directs the formation of an unique protein which will do the cellular work

21. REPLICATION OF DNA

22. DNA REPLICATION REPLICATION: Process by which DNA is copied When during the cell cycle is the DNA copied? Result: Each new cell contains a complete, exact copy of DNA of the parent cell

23. STEPS IN DNA REPLICATION STEP 1 Helix unwinds and unzips making Y- shaped “replication forks”

24. STEPS IN DNA REPLICATION STEP 2 Nucleotides base pair with the parent DNA strands Attach with H bonds Use base paring rules A-T, G-C DNA Polymerase makes the covalent bonds to join the backbone

25. STEPS IN REPLICATION Two new identical helixes form each with one parent strand and one daughter strand Semi-conservative replication