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DNA and RNA

Chapter 12. DNA and RNA. 1928 – Griffith Discovered bacteria transferred something between them that changed them into a new strain. Called this “bacterial transformation”. Historical Development. Griffith’s Experiment. Section 12-1.

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DNA and RNA

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  1. Chapter 12 DNA and RNA

  2. 1928 – Griffith • Discovered bacteria transferred something between them that changed them into a new strain. • Called this “bacterial transformation”. Historical Development

  3. 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)

  4. 1944 – Avery • Determined the transforming factor was DNA. • He destroyed different parts of the bacteria, and only when the DNA was destroyed did transformation not occur. Historical Development

  5. 1952 – Hershey and Chase • Using a blender and bacteriophage, determined that DNA, not protein, was the genetic material. Historical Development

  6. 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

  7. 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

  8. 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

  9. 1952 – Rosalind Franklin • Used x-ray crystallography to show the structure of DNA was a helix. Historical Development

  10. 1953 – Watson and Crick • Determined the structure of DNA was a double helix, and proposed a model for DNA replication. Historical Development

  11. DNA is a chain (polymer) of nucleotides. • A nucleotide consists of a sugar, phosphate and nitrogenous base. DNA Structure

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

  13. DNA is a double helix (twisted ladder). • Two nucleotide polymers are held together by weak hydrogen bonds. • Nitrogen bases always pair up this way: • Adenine with thymine A-T • Cytosine with guanine C-G • The backbone of the ladder is alternating sugars and phosphates. • The steps of the ladder are the base pairs. DNA Structure

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

  15. 12-2 Chromosomes and DNA Replication

  16. Prokaryotic cells (bacteria) • No nucleus • Single circular chromosome • Bacterial DNA is about 1.6mm long • Eukaryotic cells (all else) • 1000X more DNA than bacteria • DNA in nucleus (protected) • Multiple chromosomes • Human DNA (combined) is over 1 meter long DNA and Chromosomes

  17. Prokaryotic Chromosome Structure Chromosome E.coli bacterium Bases on the chromosome

  18. Eukaryotic DNA is tightly packed and folded. It is wound about proteins called histones. DNA and Chromosomes

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

  20. DNA Packing

  21. A cell copies its DNA before dividing. • The DNA uncoils. • Then it “unzips” – the two strands separate along the weak hydrogen bonds. • Complimentary nucleotides are added with the help of the enzyme DNA Polymerase. • The result: two identical molecules of DNA. DNA Replication

  22. 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

  23. C:\Users\Carolyn\Videos\RealPlayer Downloads\How DNA Copies Itself.mp4 DNA Replication

  24. 12-3 RNA and Protein Synthesis

  25. DNA makes RNA makes Proteins makes You. BIG IDEA

  26. Single-stranded chain of nucleotides No thymine - its replaced by uracil Sugar is ribose, not deoxyribose RNA Structure

  27. Messenger RNA (mRNA) • Carries a copy of the genetic code (gene) for a protein into the cytoplasm. • Ribosomal RNA (rRNA) • A component of ribosomes where proteins are made. • Transfer RNA (tRNA) • Carries amino acids to the ribosome for assembly into proteins. Types of RNA

  28. The process of DNA making mRNA in the nucleus is called transcription. • A section of DNA (gene) unwinds and separates • Enzymes add complimentary RNA nucleotides to make mRNA. • mRNA leaves the nucleus and goes to a ribosome in the cytoplasm. • What is the complimentary nucleotide sequence for this DNA sequence? • DNA = A-T-T-C-G-C-G Transcription

  29. Transcription Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA

  30. C:\Users\Carolyn\Videos\RealPlayer Downloads\Transcription.flv Transcription

  31. The process of mRNA being read on a ribosome to make a protein is called translation. • mRNA attaches to a ribosome. • tRNA carries amino acids to the ribosome. • The mRNA codon (3 nucleotide sequence) matches up with a complimentary tRNAanticodon (complimentary sequence). • The amino acid is dropped off and added the growing polypeptide chain. • What is the amino acid sequence for the following mRNA sequence? See the universal genetic code chart… • mRNA = AUAAGCGCU Translation

  32. The Genetic Code

  33. Translation

  34. Figure 12–18 Translation (continued)

  35. C:\Users\Carolyn\Videos\RealPlayer Downloads\Translation.flv Translation

  36. C:\Users\Carolyn\Videos\RealPlayer Downloads\From DNA to Protein.mp4 Transcription and Translation

  37. C:\Users\Carolyn\Videos\RealPlayer Downloads\DNA Transcription and Protein Assembly.mp4 Transcription and Translation

  38. Proteins are made of several polypeptide chains folded together. • The shape is important to how the protein functions. • One gene codes for the production of one polypeptide. • Therefore, several genes are needed to make one protein. Genes and Proteins

  39. 12-4 Gene Mutations

  40. Mistakes made when DNA is copied are called mutations. Two kinds: gene and chromosome mutations Kinds of Mutations

  41. Gene mutations affect only one gene. • There is a change in the sequence of bases in DNA. • This causes the protein made by that gene to be incorrect. (sometimes) • Ex: lactose intolerance Gene Mutations

  42. Changes in the number or structure of chromosomes are called chromosome mutations. • Ex: An extra chromosome causes Down Syndrome. Chromosome Mutations

  43. Substances that can cause mutations are called mutagenic agents. • UV light, chemicals, radiation Mutagens

  44. Inherited only if the mutation occurs in a sex cell. • Harmful mutations – cause many genetic disorders. • Ex: cystic fibrosis • Neutral mutations – have no effect on gene expression or protein function (most). • Beneficial mutations – source of genetic variability. • Breeders artificially select for these traits Significance of Mutations

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