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CHAPTER 12 DNA and RNA

CHAPTER 12 DNA and RNA. Essential Questions. How do genes work? What are they made of and how do they determine the characteristics of organisms? Are genes single molecules or are they longer structures made up of many molecules?. 12-1 DNA. Griffith and Transformation

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CHAPTER 12 DNA and RNA

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  1. CHAPTER 12DNA and RNA

  2. Essential Questions • How do genes work? • What are they made of and how do they determine the characteristics of organisms? • Are genes single molecules or are they longer structures made up of many molecules?

  3. 12-1 DNA Griffith and Transformation • 1928, Frederick Griffith, investigated pneumonia • Two different pneumonia bacteria • Colonies with rough edges- harmless • Colonies with smooth edges- pneumonia

  4. Rough Smooth

  5. Smooth

  6. Smooth Rough

  7. Transformation- when a bacteria picks up foreign DNA. This changes the bacteria. • Griffith’s hypothesis- • 1) some factor was transmitted from the heat-killed cells to the harmless living cells. • 2) This factor must contain information that would change the harmless cells into disease-causing cells. • 3) This factor could be passed onto offspring

  8. Oswald Avery, 1944 Smooth Destroy: Proteins Lipids Carbohydrates RNA Rough

  9. Oswald Avery, 1944 Smooth Destroy: DNA Rough

  10. Avery’s conclusion • DNA must store and transmit genetic information from one generation to the next

  11. Hershey-Chase Experiment • Alfred Hershey and Martha Chase, 1952 • What transmits hereditary information: DNA or proteins? • Bacteriophage- a virus that infects bacteria • Composed of DNA or RNA core • Protein coat

  12. A bacteriophage will inject virus DNA or RNA into a bacteria. The viral genes will use the cell to make more viruses and also destroy the cell.

  13. Components and Structure of DNA

  14. Components Structure of DNA • 5-carbon sugars • Deoxyribose • Phosphates • Nitrogenous bases

  15. Components Structure of DNA Nucleotide: • 5-carbon sugar (deoxyribose) • Phosphate • Nitrogenous base

  16. Nitrogenous bases Purines (2 rings): • Adenine • Guanine Pyrimidines (1 ring): • Cytosine • Thymine

  17. Chargaff’s Rule • Erwin Chargaff % of Guanine = % of Cytosine % of Adenine = % of Thymine

  18. Rosalind Franklin • Early 1950s • Used x-ray diffraction to Study the structure of DNA

  19. James Watson and Francis Crick 1953 created a model to explain the structure of DNA They used Franklin’s photographs

  20. Double Helix • 2 strands wrapped around each other

  21. Nucleotides are linked together • G bind to C • T binds to A • Bases are connected to opposite bases by hydrogen bonds • G to C by three bonds • T to A by two bonds

  22. 12-2 Chromosomes and DNA Replication DNA Prokaryotes- one single chromosome, DNA is circular Eukaryotes- multiple chromosomes, DNA is linear

  23. DNA Length E. Coli 4,600,000 base pairs 4,000 genes 1.6mm long Human DNA 3,000,000,000 base pairs 35,000 genes 2 meters long

  24. Chromatin- substance of tightly packed DNA and protein

  25. Histones- protein that DNA is coiled around • Nucleosome-histone with DNA wrapped around it

  26. What do histones and nucleosomes do? • Histones: • DNA held tightly= turned off • DNA held loosely= turned on Nucleosomes: aid in folding and packing of DNA

  27. DNA Replication • Prokaryotes- one site to begin replication

  28. DNA Replication • Prokaryotes- two complete complementary DNA strands created.

  29. DNA Replication • Eukaryotes- multiple sites along the linear DNA strand begin replication

  30. DNA Replication • Complementary bases are added to the template strand. CATGTGATCATAGATA- template strand

  31. DNA Replication • Complementary bases are added to the template strand. CATGTGATCATAGATA- template strand GTACACTAGTATCTAT- copied strand

  32. DNA Replication • DNA is unwound by an enzyme- Helicase • Helicase breaks the hydrogen bonds between bases • Replication bubble- Where the helicase unwinds the DNA to begin copying

  33. Replication fork- The end of the bubble where DNA is being unwound.

  34. DNA Replication • DNA polymerase- an enzyme that adds new nucleotides on the complementary strand • DNA polymerase- proof reads the new strand to make sure no mistakes are made. It ensures that the right base is added on the complementary strand. CATGTGATCATAGATA- template strand GTACACT - copied strand G A G G A T C C T G T C G A C A T T T A C G C G G

  35. 12-3 RNA and Protein Synthesis • Genes- coded DNA instructions that control the production of proteins within the cell

  36. The Structure of RNA • Similarities between RNA and DNA • Both are composed of nucleotides (5-carbon sugar, phosphate, nitrogenous base)

  37. Differences between RNA and DNA • 1. 5-carbon sugar is ribose (not deoxyribose)

  38. Differences between RNA and DNA • 2. Usually single stranded (not double stranded)

  39. Differences between RNA and DNA • 3. Contains uracil instead of thymine

  40. Types of RNA • Messenger RNA (mRNA) • Contains instructions for assembling amino acids into proteins • Long single strand of RNA

  41. Types of RNA • Ribosomal RNA (rRNA) • Proteins and rRNA make up ribosomes • Amino acids are linked together to make proteins at the ribosome.

  42. Types of RNA • Transfer RNA (tRNA) • A molecule that carries an amino acid to a ribosome in order to make a protein

  43. Transcription Transcription- Transcribing a DNA sequence into an RNA sequence • RNA polymerase- separates DNA strands and copies one strand of the DNA. It creates a complementary strand of RNA.

  44. How does RNA polymerase know where to copy? • RNA polymerase starts copy by binding to promoter- a specific sequence of DNA • RNA polymerase stops copying when it reaches a terminator- a specific sequence of DNA

  45. Transcription • RNA polymerase creates a mRNA (messenger RNA). • The mRNA strand is complementary for the DNA sequence from which it was copied. It has “U” instead of “T”. RNA- GUACCAUGAUCAUG DNA- CATGGTACTAGTAC

  46. mRNA editing The mRNA is edited: 5’ Cap- A cap is added to the front. It includes a Guanine and three phosphates. Poly A Tail- A tail is added to the end. It is a long string of “A” nucleotides. 5’ G-P-P-P- CAGUAGAUCAUGA-AAAAAAAA

  47. mRNA editing The mRNA is edited: Introns- parts of the mRNA that are cut out Exon- parts of the mRNA that are left in 5’ G-P-P-P- CAGUCGUACUAUGACACUAGAUCAUGA-AAAAAAAA 5’ G-P-P-P- CAGUCUGACAC AUGA-AAAAAAAA 5’ G-P-P-P- CAGUCUGACACAUGA-AAAAAAAA

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