1. What is the name of this monomer?

1. Warm Up 1. What is the name of this monomer? 2. What is the name of the polymer or macromolecule to which this monomer belongs?

2. The Structure of DNA

3. DNA • DNA is often called the blueprint of life. • In simple terms, DNA contains the instructions for making proteins within the cell.

4. Why do we study DNA? We study DNA for many reasons, e.g., • its central importance to all life on Earth, • medical benefits such as cures for diseases, • better food crops.

5. DO PROTEINS CARRY THE GENETIC CODE? At the time most scientists believed that _________ had to be the molecules that made up genes. There were so many different kinds proteins and DNA seemed to be too monotonous . . . repeating the same ___ subunits. proteins 4

6. GENETIC MATERIAL In the middle of the 1900’s scientists were asking questions about genes. What is a gene made of? How do genes work? How do genes determine characteristics of organisms?

7. 1928 – Frederick Griffith looked at pneumonia bacteria trying to figure out what made people die R (Rough) strain -mice lived S (SMOOTH) strain - killed mice

8. . . . mice lived. If he heated the LETHAL strain first _______________ The heat killed bacteria were no longer LETHAL.

9. BUT. . . If he mixed heat-killed LETHAL bacteria with live harmless bacteria ________________ . . . mice DIED ! When he looked inside dead mice, he found ______________ bacteria! Somehow the heat killed LETHAL bacteria passed their characteristics to the harmless bacteria. LIVE LETHAL

10. TRANSFORMATION Griffith called this process __________________ because one strain of bacteria had been changed permanently into another. But what was the factor that caused the transformation? A protein ? A lipid ? A carbohydrate ? A nucleic acid ?

11. 1944- Oswald Avery’s team of scientists repeat Griffith’s experiments looking for the transforming molecule. After heat killing the LETHAL Pneumonia bacteria, he treated them with digestive enzymes that destroy specific kinds of molecules. If proteins, polysaccharides, lipids, or RNA’s were destroyed .. . ______________________________ Transformation still occurred!

12. DNA But when they treated the heat-killed LETHAL bacteria with enzymes to destroy _____ there was NO transformation! . . . the mice lived! DNA was the molecule that caused the genetic change.

13. GRIFFITH EXPERIMENT (PNEUMONIA-RAT) Showed ____________ could be passed between bacteria & cause a change. AVERY EXPERIMENT(Digestive enzymes) showed that the genetic material was _____ genetic material DNA

14. Scientists are skeptical… it takes more than one experiment to convince them. 1952-Alfred Hershey and Martha Chase experimented with viruses that infect bacteria = _________________ Knew bacteriophages were made of ________ and _______ bacteriophages proteins DNA

15. http://www.mun.ca/biology/scarr/hersheychase-experiment.jpg

16. ALFRED HERSHEY& MARTHA CHASE (1952) • CONCLUDED THAT THE GENETIC MATERIAL OF THE BACTERIOPHAGE WAS DNA, NOT PROTEIN • USED RADIOACTIVE PHOSPHOROUS AND SULFUR

17. HERSHEY-CHASE BLENDER EXPERIMENT only DNA not protein Showed_______________ entered cell during infection. Conclusion: ______________in virus was _____ not protein Genetic material DNA

18. BACTERIAL VIRUSES

19. Chargaff, Erwin • discovered a relationship in the nitrogenous bases • ADENINE (A) = THYMINE (T) GUANINE (G) = CYTOSINE (C)

20. Rosalind Franklin (1952) • TOOK AN X-RAY OF THE DNA STRUCTURE SO THE PATTERNS COULD BE SEEN • THE X-RAYS SHOW THAT DNA IS TWISTED AROUND EACH OTHER LIKE A HELIX AND HAS 2 STRANDS

21. Watson and Crick (1953) • STUDIED THE STRUCTURE OF DNA BY BUILDING A 3-DIMENSIONAL MODEL OF THE MOLECULE AFTER USING CLUES FROM FRANKLIN’S X-RAY OF DNA.

22. DNA Replication • Watson & Crick Discovered in 1953 • Structure of DNA • How DNA can be copied & replicated. • Each strand of DNA is a mirror image of the other strand • Strands areComplimentary

23. The nucleus of a cell contains chromosomes

24. The earth is 150 billion m or 93 million miles from the sun. DNA by the Numbers • Each cell has about 2 m of DNA. • The average human has 75 trillion cells. • The average human has enough DNA to go from the earth to the sun more than 400 times. • DNA has a diameter of only 0.000000002 m.

25. DNA & Chromosomes • DNA Location • Prokaryotes – Cytoplasm • Single Circular Molecule • Eukaryotes – Nucleus • Multiple Chromosomes • Humans 46 • Drosophila 8 • Giant Sequoia 22

26. DNA Length • E. coli (Gram Neg. Bacilli) 4,639,221 Base Pairs 1.6 mm long which must fit in a bacteria 1.6 um wide, or 1/1000 the length of the DNA strand • Human DNA 1000 times larger • Tightly Packed

27. Chromosome Structure Each Human Cell Contains More Than A 6 feet of DNA • Tightly Packed Into Chromatin DNA + Protein = Chromatin DNA Coiled Around Proteins Called Histones • Forms Beads Called Nucleosomes

28. Chromosome Structure • Nucleosomespack together to form a thick fiber containing loops and curls Usually loose, diffuse Condense during Mitosis & Meiosis Fold enormous lengths of DNA into the tiny nucleus

29. Chromosome Structure Histones proteins that have very low mutation rates Appears most mutations have been lethal – therefore, eliminated Regulate “reading” of chromosome

30. THINK ABOUT IT How could you get this piece of string into the container? http://www.artzooks.com/files/3966/AZ533823_320.jpghttp://www.mivaroo.com/sites/toyconnection.com/

31. The Structure of DNA • DNA is a polymer made up of repeating monomers of nucleotides. • DNA determines an organism’s traits by controlling the manufacturing of proteins. • The sequencing of nucleotides--baseparings--makes us unique and individual---makes me different from you!

32. NUCLEIC ACIDS are built from subunits called ____________________ NUCLEOTIDES SUGAR in DNA is ________________ DEOXYRIBOSE

33. “Rungs of ladder” Nitrogenous Base (A,T,G or C) “Legs of ladder” Alternating Phosphate & Deoxyribose Backbone DNA Double Helix

34. 4 DIFFERENT NUCLEOTIDES

35. Each nucleotide is constructed of 3 parts: a PHOSPHATE group, a SUGAR molecule, & 1 of 4 nitrogen bases Adenine (A) Guanine (G) Cytosine (C) Thymine (T) purines pyrimidines

36. PURINE + PURINE: TOO WIDE PYRIMIDINE + PYRIMIDINE: TOO WIDE PURINE + PYRIMIDINE: WIDTH CONSISTENT WITH X-RAY DATA

37. Because of the hydrogen bonds, e Adenine can only bond with Thymine e & Guanine can only bond with Cytosine e *A purine is always paired with a pyrimidine.* e

38. This is known as COMPLEMENTARY base pairing http://www.biology.washington.edu/fingerprint/dnapair.gif

39. O -P O O -P O O -P O O O O O O O C C ribose ATP Nucleotides One deoxyribose together with its phosphate and base make a nucleotide. Nitrogenous base O Phosphate C C C Deoxyribose O

40. For example: • TCG AAC TGG • AGC TTG ACC • You try: • CCA GAT TGA GGT CTA ACT

41. Mini Quiz!! • What 2 scientists constructed a model of DNA and published their results in 1953? • If one strand of DNA read ATC GTA, what would the other strand read?

42. Duplicating DNA Replication Duplication of the DNA in preparation for cell division ( S phase of Interphase ) Prokaryotes Replication starts at a single point and proceeds in opposite directions Eukaryotes Occurs at multiple points on multiple chromosomes at once

43. S phase DNA replication takes place in the S phase. G1 G2 interphase Mitosis -prophase -metaphase -anaphase -telophase Synthesis Phase (S phase) • S phase during interphase of the cell cycle • Nucleus of eukaryotes

44. DNA Replication • Copying process by which a cell duplicates its DNA • DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing • Each strand of the double helix of DNA serves as a template for the new strand

46. 3’ Parental DNA Molecule 5’ Replication Fork 3’ 5’ DNA Replication • Begins atOrigins of Replication • Two strands open forming Replication Forks (Y-shaped region) • New strands grow at the forks

47. DNA Replication Enzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds Single-Strand Binding Proteinsattach and keep the 2 DNA strands separated and untwisted

48. How Replication Occurs Enzymes Involved Named For The Reactions They Catalyze DNA Polymerase • Polymerizes individual nucleotides • Proof Reads each new DNA strand

49. Figure 12–11 DNA Replication Original strand Section 12-2 DNA polymerase New strand DNA polymerase Growth Growth Replication fork Replication fork Nitrogenous bases New strand Original strand Sites where strand separation and replication occur are called _____________ replication forks

50. Proofreading New DNA • DNA polymerase initially makes about 1 in 10,000 base pairing errors • Enzymes proofread and correct these mistakes • The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors