1. Fig. 16-1

2. DNA – lots of it in a small space

4. DNA – A Historical Perspective 1865 – Gregor Mendel – “Father of Heredity” 1869 – Johann Miescher (Swiss biochemist) – isolates DNA from WBC 1902 – Walter Sutton – American Geneticist – Columbia U. Theory of the Chromosome 1928 – Frederick Griffith – British Bacteriologist – discovers transformational factor 1944 – Oswald Avery et al. - Canadian-born American physician – shows that the transformational factor was not a protein but DNA 1952 – Alfred Hershey & Martha Chase – provide conclusive evidence that DNA is the transformational factor 1952 – Rosalind Franklin & Maurice Wilkins – use x-ray diffraction to analyze DNA 1953 – James Watson & Francis Crick construct double helix model of DNA

5. Johannes Friedrich Miescher 1844-1895 In 1869, first to isolate a substance he called nuclein from the nuclei of leucocytes or WBC Collected these from pus he obtained from bandages at nearby hospitals. He found that nuclein contained phosphorus and nitrogen, but not sulfur

6. Walter Sutton (1877-1916) American geneticist & physician – Columbia University Boveri-Sutton Chromosome Theory Made connection – Mendel’s Laws of Heredity could be applied to chromosomes at the cellular level of living organisms

7. Thomas Hunt Morgan (1866-1945) American geneticist and embryologist – Columbia U. Studied the mutations in fruit flies, Drosophilia melanogaster demonstrated that genes are carried on chromosomes and are the mechanical basis of hereditygeneschromosomes Nobel Prize in Physiology or Medicine in 1933

8. Frederick Griffith 1871 - 1941 What is the transformational factor??? Is it DNA or Protein??? Griffith’s research, working with two strains of a bacterium, one pathogenic and one harmless, addresses this vital question In 1941, Griffith was killed at work in his London laboratory as a result of an air raid in the London Blitz.

9. DNA – A Historical Perspective Griffith and Transformation 1928 – British pathologist was researching How certain types of bacteria produced pneumonia He isolated 2 different strains: R which was harmless and S - virulent

10. Live S-strain kills mouse

11. Injection of Rough Colonies ( R) Results in Live Mice

12. Heat-killed Smooth colonies (S) Result in Live Mice

13. Heat-Killed S + Live R = Dead Mice

14. Fig. 16-2 Living S cells (control) Living R cells (control) Heat-killed S cells (control) Mixture of heat-killed S cells and living R cells Mouse dies Mouse healthy Living S cells RESULTS EXPERIMENT

15. Oswald Avery and DNA (1944) Working along with Colin Macleod & Maclyn McCarty Repeated Griffith’s work with modifications Which molecule in the heat-killed was the transformational factor? The components of the Ground up S were isolated, each mixed with R and injected into mice

16. In 1952, Alfred Hershey and Martha Chase performed experiments showing that DNA is the genetic material of a phage known as T2 To determine the source of genetic material in the phage, they designed an experiment showing that only one of the two components of T2 (DNA or protein) enters an E. coli cell during infection They concluded that the injected DNA of the phage provides the genetic information Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Animation: Hershey-Chase Experiment Animation: Hershey-Chase Experiment Alfred Hershey and Martha Chase. 1953 Alfred Hershey and Martha Chase. 1953

17. Fig. 16-3 Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm

18. Fig. 16-4-1 EXPERIMENT Phage DNA Bacterial cell Radioactive protein Radioactive DNA Batch 1: radioactive sulfur ( 35 S) Batch 2: radioactive phosphorus ( 32 P)

19. Fig. 16-4-2 EXPERIMENT Phage DNA Bacterial cell Radioactive protein Radioactive DNA Batch 1: radioactive sulfur ( 35 S) Batch 2: radioactive phosphorus ( 32 P) Empty protein shell Phage DNA

20. Fig. 16-4-3 EXPERIMENT Phage DNA Bacterial cell Radioactive protein Radioactive DNA Batch 1: radioactive sulfur ( 35 S) Batch 2: radioactive phosphorus ( 32 P) Empty protein shell Phage DNA Centrifuge Pellet Pellet (bacterial cells and contents) Radioactivity (phage protein) in liquid Radioactivity (phage DNA) in pellet

21. Fig. 16-6 (a) Rosalind Franklin (b) Franklin’s X-ray diffraction photograph of DNA

25. Erwin Chargaff (1905-2002) and “Chargaff’s Rules” The bases were not present in equal quantities They varied from organism to organism. No matter where DNA came from — yeast, people, or salmon — the number of adenine bases always equaled the number of thymine bases and the number of guanine always equaled the number of cytosine bases. He published a review of his experiments in 1950, calling the ratios — which came to be known as Chargaff’s Rules

26. Chargaff’s rules state that in any species there is an equal number of A and T bases, and an equal number of G and C bases Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

29. Fig. 16-8 Cytosine (C) Adenine (A)Thymine (T) Guanine (G)

30. Fig. 16-UN2 Sugar-phosphate backbone Nitrogenous bases Hydrogen bond G C A T G G G A A A T T T C C C

31. Fig. 16-7a Hydrogen bond 3 end 5 end 3.4 nm 0.34 nm 3 end 5 end (b) Partial chemical structure(a) Key features of DNA structure 1 nm

32. Fig. 16-5 Sugar–phosphate backbone 5 end Nitrogenous bases Thymine (T) Adenine (A) Cytosine (C) Guanine (G) DNA nucleotide Sugar (deoxyribose) 3 end Phosphate Purines Adenine Guanine PurAsGold Pyrimidines Cytosine Thymine Uracil PyCUT Carbon 1 – bonds to nitrogen base Carbon 3 – bonds to next nucleotide Carbon 5 – bonds to phosphate group

33. Fig. 16-UN1 Purine + purine: too wide Pyrimidine + pyrimidine: too narrow Purine + pyrimidine: width consistent with X-ray data

34. Additional Evidence That DNA Is the Genetic Material It was known that DNA is a polymer of nucleotides, each consisting of a nitrogenous base, a sugar, and a phosphate group In 1950, Erwin Chargaff reported that DNA composition varies from one species to the next This evidence of diversity made DNA a more credible candidate for the genetic material Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Animation: DNA and RNA Structure Animation: DNA and RNA Structure

35. Building a Structural Model of DNA: Scientific Inquiry After most biologists became convinced that DNA was the genetic material, the challenge was to determine how its structure accounts for its role Maurice Wilkins and Rosalind Franklin were using a technique called X-ray crystallography to study molecular structure Franklin produced a picture of the DNA molecule using this technique Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

36. Franklin’s X-ray crystallographic images of DNA enabled Watson to deduce that DNA was helical The X-ray images also enabled Watson to deduce the width of the helix and the spacing of the nitrogenous bases The width suggested that the DNA molecule was made up of two strands, forming a double helix Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Animation: DNA Double Helix Animation: DNA Double Helix

37. Watson and Crick built models of a double helix to conform to the X-rays and chemistry of DNA Franklin had concluded that there were two antiparallel sugar-phosphate backbones, with the nitrogenous bases paired in the molecule’s interior Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

38. At first, Watson and Crick thought the bases paired like with like (A with A, and so on), but such pairings did not result in a uniform width Instead, pairing a purine with a pyrimidine resulted in a uniform width consistent with the X-ray Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

39. Watson and Crick reasoned that the pairing was more specific, dictated by the base structures They determined that adenine (A) paired only with thymine (T), and guanine (G) paired only with cytosine (C) The Watson-Crick model explains Chargaff’s rules: in any organism the amount of A = T, and the amount of G = C Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

40. Concept 16.2: Many proteins work together in DNA replication and repair The relationship between structure and function is manifest in the double helix Watson and Crick noted that the specific base pairing suggested a possible copying mechanism for genetic material Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

41. Fig. 16-9-1 A T G C TA TA G C (a) Parent molecule

42. Fig. 16-9-2 A T G C TA TA G C A T G C T A T A G C (a) Parent molecule (b) Separation of strands

43. Fig. 16-9-3 A T G C TA TA G C (a) Parent molecule AT GC T A T A GC (c) “Daughter” DNA molecules, each consisting of one parental strand and one new strand (b) Separation of strands A T G C TA TA G C A T G C T A T A G C

44. The Basic Principle: Base Pairing to a Template Strand Since the two strands of DNA are complementary, each strand acts as a template for building a new strand in replication In DNA replication, the parent molecule unwinds, and two new daughter strands are built based on base-pairing rules Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Animation: DNA Replication Overview Animation: DNA Replication Overview

45. Fig. 17-5 Second mRNA base First mRNA base (5 end of codon) Third mRNA base (3 end of codon)

46. Enzymes involved in DNA Replication & Transcription EnzymeFunction Helicase“molecular zipper” – unwinds double helix; breaks hydrogen bonds that holds base pairs together Topoisomerase (gyrase)“molecular swivel”- relieves overwinding stress on DNA strands by working ahead of helicase and breaking, swiveling and rejoining small sections of the DNA molecule DNA polymeraseUsing a parent DNA strand, adds free- floating nucleotides (A, T, G, & C’s) covalently to the new strand being constructed. ligase“molecular glue” – joins fragments of the New DNA strand together RNA polymerase (used in transcription)Uses one strand of DNA as a template to construct mRNA – adds free-floating nucleotide EditaseFixes mistakes on DNA molecule