1. KEY CONCEPT DNA structure is the same in all organisms.

2. If you unraveled all your chromosomes from all of your cells and laid out the DNA end to end, the strands would stretch from the Earth to the Moon about 6,000 times. 2

3. Let’s Review! What is a macromolecule? What are the four kinds of organic molecules? What are nucleic acids made of? 3 - A large organic molecule (made of carbon!) - Carbohydrates, lipids, proteins and nucleic acids - NUCLEOTIDES = Phosphate group, 5-carbon sugar, nitrogenous base

4. Nucleic Acids are the chemical link between generations dating back to the beginning of life on earth. 4

5. A nucleic acid is a complex macromolecule that stores information in cells in the form of a code. 5

6. DNA What are genes made of? Where are genes located? How do they determine characteristics?

7. Try to figure out what happened? HarmlessDisease-causing Heat-killed Harmless & Heat- bacteriabacteria disease causing killed disease causing

8. Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease- causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumoniaLives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia Section 12-1 Figure 12–2 Griffith’s Experiment Go to Section:

9. Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease- causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumoniaLives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia Section 12-1 Figure 12–2 Griffith’s Experiment Go to Section:

10. Some History While Frederick Griffith was experimenting with pneumonia, he discovered that mice injected with dead bacteria still died of pneumonia… so it was something inside the bacteria that was still passed on to the next generation. Oswald Avery and other scientists discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation of an organism to the next.

11. Some More History Alfred Hershey and Martha Chase concluded that the genetic material of the bacteriophage (a virus that “eats” bacteria) is DNA, not protein.

12. Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1 Go to Section:

13. Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1 Go to Section:

14. Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1 Go to Section:

15. DNA Genes are made of DNA = deoxyribonucleic acid How could DNA code for everything genes do? –Genes had to carry information from one generation to the next –Genes had to put that information to work by determining the inheritable characteristics of organisms –Genes had to be easily copied, because it is replicated every time the cell divides

16. DNA Structure Double Helix (twisting ladder) modeled by Watson & Crick 1953 Sides/backbone - alternating deoxyribose sugar & phosphate “Rungs” - nitrogen bases held together by hydrogen bonds

17. The Double Helix Rosaline Franklin’s x-ray showed that two DNA strands are twisted around each other. James Watson and Francis Crick used Franklin’s x-ray to make a model of DNA. Watson and Crick’s model of DNA was a double helix, in which two strands were wound around each other. Watson and Crick also discovered that hydrogen bonding held the nitrogenous bases together.

19. DNA DNA = DeoxyriboNucleic AcidDNA = DeoxyriboNucleic Acid –Short nucleic acid –A polymer that stores genetic information –Found in the chromosomes of all organisms –Controls production of proteins depending on sequence of nitrogen bases –Unit of structure = nucleotide

20. DNA Nucleotide – 3 partsNucleotide – 3 parts 1.A phosphate group – PO 4 2.A 5 carbon sugar – deoxyribose 3.A nitrogen base Draw the Picture

21. Base Pairing Base Pairing According to Chargaff’s Rule The complementary bases always pair a certain purine with a certain pyrimidine Base Base A = adenine A = adenine T = thymine T = thymine C = cytosine C = cytosine G = guanine G = guanine Complementary Base thymine thymineadenineguaninecytosine

22. Base Pairing Rule: –A always pairs with T –C always pairs with G Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

23. Nitrogen Bases Nitrogen Bases – name source for the nucleotidesNitrogen Bases – name source for the nucleotides 2 different types:2 different types: –Purines – double ring AdenineAdenine GuanineGuanine –Pyrimidines – single ring CytosineCytosine ThymineThymine

24. Nitrogen Bases PurinesPyrimidines AdenineGuanine CytosineThymine Phosphate group Deoxyribose

25. DNA Structure Phosphate Group Deoxyribose Sugar Nitrogenous Base Weak Hydrogen Bonds

27. Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Figure 12–7 Structure of DNA Section 12-1 Go to Section:

28. Let’s pair up DNA! What would pair up with ATCG? TAGC What would pair up with ATTAGC? TAATCG What would pair up with ATACGGTC? TATGCCAG

29. Replication – General Info The exact copying of DNAThe exact copying of DNA DNA must be copied before cells divide  each daughter cell has a complete set of DNADNA must be copied before cells divide  each daughter cell has a complete set of DNA Original strands serve as templates for new strandsOriginal strands serve as templates for new strands Replication occurs in both directionsReplication occurs in both directions

30. Replication – General Info How it happens: 1.Helicase (enzyme) unwinds the DNA by breaking hydrogen bonds

31. 2. DNA polymerase (enzyme) joins individual nucleotides to each separated strand, producing DNA molecule **DNA polymerase also proofreads each new DNA strand to make perfect copies

32. Results of Replication 2 DNA molecules  each contains one original strand & one new strand (semi-conservative) strand & one new strand (semi-conservative)

34. Review of The Genetic Code The sequence of nitrogen bases (A,T,C & G) along a DNA strand code for the synthesis (making) of specific proteins. According to Chargaff’s Rule: –A bonds with T –C bonds with G

35. What are chromosomes??? 35 Nucleotides make up DNA DNA winds into Chromatin Chromatin condenses into Chromosomes Chromosomes contain Genes Genes are sections of DNA THAT CODE FOR PROTEINS Chromosomes contain Instructions for making YOU!!!

36. outsideProteins are made in the ribosomes outside the nucleus. DNA is copied (replicated) in the nucleus but cannot leave the nucleus. THEREFORE……. A message must be sent to the ribosomes in the cytoplasm telling them what proteins to make. This message is carried by a nucleic acid called messenger (mRNA ).

37. RNA Structure 1.RNA is a single strand 2.RNA has the sugar ribose 3.Adenine bonds with Uracil (NOT thymine). 4.Can leave the nucleus RNA differs from DNA in 4 ways:

38. Differences Between DNA Deoxyribose Sugar Double Stranded A, C, T, G Remains in nucleus RNA Ribose sugar Single Stranded A, C, U, G Moves out of nucleus

39. 2. Which scientists came up with the double helix model of DNA? 1. How many strands does DNA have? a. Hershey & Chase c. Galileo & Aristotle b. Watson and Crick d. Darwin & Malthus a. oneb. two c. threed. four Let’s wrap it up with a few questions together…

40. 3. What holds the strands of DNA together? 5. What DNA bases would pair up with GAATCC? c. CGGAGG a. CTTAGG d. GCCTCC b. GAATCC a. Phosphate Groupb. Deoxyribose Sugar c. Hydrogen Bonds d. Nitrogen bonds 4. What DNA bases would pair up with CATTAT? a. CATTATb. TATTAC c. GTAATA d. GUAAUA

41. Is your answer the same as earlier… What are genes made of?