Unraveling DNA & Genetic Transformation: Griffith, Avery, Hershey & Chase Experiments

1. Chapter 12 DNA & RNA

2. I.DNA • A. Griffith & Transformation • Frederick Griffith was trying to figure out how bacteria made people sick-how they cause a certain type of pneumonia. • He isolated 2 strains(types) from mice-both cultured well,but only one caused pneumonia.The culture of the disease causing bacteria were __________________colonies while the other was rough. smooth

3. 1-Griffith’s experiments (1928) • Mice injected w/ disease –causing strain got sick and died and nothing happened if injected w/other strain…He wondered if the disease-causing type made a toxin…? • So he took some of disease strain and heated to kill bacteria and then injected into mice….mice survived suggesting it was not a toxin producing disease

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

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

6. 2-Transformation • He mixed his heat –killed w/ live harmless bacteria and injected into mice…..________________________ • Somehow the disease –causing strain passed their disease capacity to harmless bacteria….. disease –causing strain found in lungs • He called this changing of one bacteria by the genes of another _____________________....Thus a factor(gene) from heat killed disease –causing strain was passed on. Mice developed pneumonia transformation

7. B. Avery & DNA • Team of scientists lead by Avery in 1944 repeated Griffith’s experiment in order to determine which molecule was responsible for the transformation. • They made an extract from the heat-killed bacteria and treated it w/enzymes that kill proteins,lipids and other molecules,inc. RNA

8. Avery cont’d transformation • ____________________still occurred so the above molecules were not responsible for transformation • They repeated the experiment but used enzymes that kill____________, stopping transformation…. • Therefore ________caused the transformation and thus stores and transmits genetic info DNA DNA

9. C. The Hershey –Chase Experiment • 1952-Alfred Hershey and Martha Chase studied viruses-disease-causing particles smaller than a cell. • ______________________-virus that infects bacteria.They have a DNA or RNA core and a protein coat…They attach to the surface of a bacterium and inject genetic info into cell.The viral genes act to produce many new bacteriophages and eventually destroy bacterial cell,w/_____________bursting out. viruses bacteriophage

10. They grew viruses in cultures containing _________________________________,mixed them w/bacteria and waited a few min. for viruses to inject genetic material. • Then they separated the bacteria from the viruses and tested bacteria for radioactive marker…..nearly all the radioactivity was P-32-found in _________----thus concluding it was the genetic material was DNA ! Radioactive markers DNA

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

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

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

14. D. The Components and Structure of DNA • Scientists questioned how the DNA molecule could do three things 1)carry info from 1 generation to the next 2)putting that info to work and 3)could be easily copied • DNA is a long molecule made of units called ___________________________________________- nucleotides

15. The nucleotide is made of 3 basic parts:______________________(sugar), a phosphate group and a_________________________________ deoxyribose Nitrogenous base

16. 2 nitrogenous bases are purines(have 2 rings):___________________________(A)and_______(G) • 2 other nitrogenous bases are pyrimidines (have 1 ring):____________________(C)and ____________________________(T) Cytosine and thymine Adenine ,guanine --backbone made by sugar and phosphate w/ bases sticking out sideways

17. Figure 12–5 DNA Nucleotides Section 12-1 Purines Pyrimidines Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose

18. 1-_______________________Rules-discovered that %’s of Cytosine and guanine were almost equal in DNA and the same was true for adenine and thymine….Thus A pairs w/T and C w/ G-BASE PAIRING Chargaff’s Rules

19. Percentage of Bases in Four Organisms Section 12-1 Source of DNA A T G C Streptococcus 29.8 31.6 20.5 18.0 Yeast 31.3 32.9 18.7 17.1 Herring 27.8 27.5 22.2 22.6 Human 30.9 29.4 19.9 19.8

20. 2- X-ray evidence-1950’s –Rosalind Franklin used X-ray diffraction to learn about DNA structure----The scattered X pattern seen begins to show the __________-partial TWISTED STRUCTURE of DNA helix

21. 3---Double helix_ • Watson and Crick -2 strands wound around each other---like the twisted ladder or spiral staircase • Strands held together by H-bonds

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

24. Interest Grabber Section 12-2 • A Perfect Copy • When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells.

25. I Section 12-2 1. On a sheet of paper, draw a curving or zig-zagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper. 2. Hold the papers side by side, and compare the lines. Do they look the same? 3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? 4. How could you use the original paper to draw exact copies of the line without tracing it? 5. Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original?

27. II. Chromosomes & DNA Replication • A-DNA & Chromosomes • In cytoplasm in prokaryotes • In _______________________found in cell nucleus in the form of a number of chromosomes(46 humans,8 Drosophilia and 22 Sequoia trees) eukaryotes

28. 1--DNA length • 1.6 mm in E.coli(has 4,639,221 base pairs)---obviously it must be tightly folded

29. 2-Chromosome Structure • Eukaryotic cells have about 1000 times as many base pairs of DNA than a bacterium • Humans cells have ~ 1 m DNA • Eukaryotic chromosomes contain DNA and a protein ,which together make _____________________-consisting of DNA tightly packed around proteins called histones chromatin

30. DNA and histone together make beadlike_____________________________ • Nucleosomes pack together to make thick fibers,drawn together during mitosis…also separating • Role of nucleosomes-fold great lengths of DNA into tiny spaces nucleosomes

35. Prokaryotic Chromosome Structure Section 12-2 Chromosome E.coli bacterium Bases on the chromosome

36. Figure 12-10 Chromosome Structure of Eukaryotes Section 12-2 Nucleosome Chromosome DNA double helix Coils Supercoils Histones

37. B. DNA Replication • Each strand of DNA double helix has all the info to___________________________by base pairing • Strands are complementary • In prokaryotes,this begins @single point and proceeds-often in 2 directions • In Eukaryotes,DNA replication begins @ 100’s of places,going both directions until complete • __________________________is where replication occurs Reconstruct the other half Replication fork

38. 1-Duplicating DNA • __________________________or duplication of DNA happens before cell division---ensuring each cell has a complete set of DNA molecules • Each strand of a double helix serves as a _____________________or model for new strand • A pairs w/ T and C w/ G template replication

39. 2-How Replication Occurs • Carried out by a series of enzymes that unzip a molecule • ____________________________________ joins individual nucleotides to make a DNA molecule….also proof reads the new strands DNA polymerase

41. Figure 12–11 DNA Replication Section 12-2 Original strand DNA polymerase New strand Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand

42. III. RNA & Protein Synthesis • The double helix structure explains how DNA is copied,but not how a gene works-_______________are coded DNA instructions that control the production of protein in the cell. • A) The structure of RNA • Long chain of nucleotides • 3 main differences between DNA & RNA: • 1--Sugar is _________________ • 2---Generally single-stranded • 3---RNA contains ________________(U) in place of thymine (T) ribose uracil genes

43. Protein synthesis B. Types of RNA • Main job=_________________-ie the assembly of amino acids into proteins • 3 Types: • ____________________(mRNA)-carry copies for instructions from DNA to rest of cell • ____________________(rRNA)-type of RNA that helps make up ribosomes,where proteins assembled • ________________(tRNA)transfers each amino acid to the ribosome as it is coded for on mRNA. messenger ribosomal Transfer

44. Messenger RNA Ribosomal RNA Transfer RNA Bringamino acids toribosome Combine with proteins tRNA mRNA Carry instructions rRNA DNA Ribosome Ribosomes Concept Map Section 12-3 RNA can be which functions to also called also called which functions to also called which functions to from to to make up

45. C. Transcription-produces RNA molecules by copying part of nucleotide sequence of DNA into a complementary sequence in RNA • Requires enzyme known as _______________________________________-binds to DNA and separates DNA strands.Then uses one strand as template to make RNA • The enzyme only binds to areas known as promoters-signals that indicate where to make RNA.Similar signals tell where to stop RNA-polymerase

46. Figure 12–14 Transcription Section 12-3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA

47. D. RNA editing • ________________________ in eukaryotic genes ,sequences of nucleotides that ARE NOT involved in coding for proteins • _______________________-DNA sequence that does code for protein exons introns

48. E. Genetic Code polypeptide • ______________________-chain of amino acids=proteins • _________________-3 consecutive nucleotides that specify a specific amino acid • Example –UCGCACGGU reads UCG_CAC_GGU and codes for Serine-Histidine-Glycine codon

49.  The Genetic Code Section 12-3