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Great Ideas in Science: Lecture 12

Great Ideas in Science: Lecture 12. Great Idea: All living things share the same genetic code. Professor Robert Hazen UNIV 301. Key Idea. All living things share the same genetic code 1. DNA carries the genetic message 2. Messenger RNA copies the DNA

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Great Ideas in Science: Lecture 12

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  1. Great Ideas in Science:Lecture 12 Great Idea: All living things share the same genetic code. Professor Robert Hazen UNIV 301

  2. Key Idea All living things share the same genetic code 1. DNA carries the genetic message 2. Messenger RNA copies the DNA 3. Transfer RNA holds an amino acid 4. Ribosomal RNA assembles a protein

  3. Classical Genetics Gregor Mendel used pea plants to discover three laws of inheritance 1. Genes exist 2. Each parent contributes half 3. Some traits are dominant and some are recessive traits

  4. Cellular Genetics • Chromosomes • Humans have 23 pairs • Mitosis (one cell becomes two) • 2 daughter cells same as parent • Most cellular division in your body • Meiosis (one becomes 4 gametes) • Crossing-Over (reshuffle = end of meiosis) • Recombination makes every gamete unique.

  5. Mitosis • Simple cell division • Observe chromosomes • Not for sexual reproduction • Process • Copy chromosomes • Separate into two cells

  6. Meiosis • Sexual reproduction • Begins like mitosis • Chromosome crossover • 1 cell forms 4 gametes • Gametes are genetically unique • ½ normal chromosomes

  7. Nucleotides: The Building Blocks of Nucleic Acids Nucleotides are made from three molecules: 1. Sugar DNA: deoxyribose RNA: ribose 2. Phosphate ion 3. Base Adenine (A) Guanine (G) Cytosine (C) Thymine (T)

  8. DNA’s Double Helix

  9. DNA Base Pairing Adenine:Thymine Cytosine:Guanine

  10. The Replication of DNA • DNA replication occurs before mitosis & meiosis • Process • DNA double helix splits • New bases bond to exposed bases • Results in two identical DNA strands

  11. How Does DNA Make Protein? • Chromosomes (DNA) • Carry the genetic message • Messenger RNA • Copies the genetic message • Transfer RNA • Holds an amino acid • Ribosomal RNA • Assembles a protein

  12. RNA Structure 1. Single strand of nucleotides 2. The sugar is ribose 3. Thymine is replaced by uracil (U), which bonds with adenine

  13. Synthesis of ProteinsStep 1: Transcription of DNAMessenger RNA (mRNA)

  14. Synthesis of ProteinsStep 2: Match tRNA to mRNATransfer RNA (tRNA)

  15. The Ribosome

  16. The Genetic Code

  17. Protein Synthesis Summary 4. Fold the amino acid chain into a protein.

  18. DNA & RNA Vocabulary • Nucleotide = one genetic letter – phosphate-sugar-base (A, T, C or G) • Codon = one 3-letter genetic word that defines an amino acid • Gene = the recipe for one protein, typically with >100 genetic words • Chromosome = a genetic cookbook with thousands of protein recipes • Genome = all of the genetic material of an organism (23 volumes for humans)

  19. From DNA to ProteinStep 1: DNA  mRNA

  20. From DNA to ProteinmRNA  tRNA  Amino Acid

  21. From DNA to ProteinStep 2: mRNA locks onto the ribosome

  22. From DNA to ProteinStep 2: mRNA locks onto the ribosome

  23. From DNA to ProteinStep 3: tRNA matches mRNA

  24. From DNA to ProteinStep 4: Amino acids link up

  25. From DNA to ProteinStep 4: Amino acids link up

  26. From DNA to ProteinRecharge the tRNA with AA

  27. Genetics – Key Concepts • Human genome project • Viruses • DNA Fingerprinting (PCR) • Behavioral Genetics • Genetic Engineering Microbes Plants Animals • Gene Therapy • Cancer

  28. Human Genome Project(Our DNA) 23 pairs of chromosomes ~ 25,000 genes; each codes for a protein ~ 3,000,000,000 base pairs (rungs of the DNA ladder)

  29. Human Genome ProjectMapping Mapping = locating the genes

  30. Human Genome ProjectSequencing Sequencing = exact sequence of A,T,C, & G

  31. Human Genome ProjectOther Organisms Mouse, Rat, Rabbit, Cat, Dog Chimpanzee, Elephant, Whale, Zebrafish Frog, Fly, Flatworm Several plants Yeast Hundreds of microbes (pathogens) Thousands of viruses Mammoth!!!

  32. Unanswered Question:Why Are Genes Expressed? All your cells contain the same genes. But not all cells have same the function. Therefore, some process must turn genes on and off. How and why are certain genes activated?

  33. 2. Viruses

  34. 2. VirusesWhat is a Virus? • A virus is a loop of genetic material (DNA or RNA) wrapped in proteins • It “infects” a cell by using the universal genetic code

  35. Viruses Viruses versus cells: Not alive, no metabolism Cannot reproduce on own Structure Short DNA or RNA Protein coating How it works Taken into cell Takes over cell Produces more copies Kills cell

  36. Viral Epidemics • Treatment of Viruses • Cannot use medication • Use vaccination • Viruses evolve rapidly • HIV • Influenza • SARS • Bird flu • H1N1

  37. 3. DNA Fingerprinting (PCR)

  38. DNA Fingerprinting • DNA fingerprinting • Analysis of DNA in human tissue • Uses • identify criminals • identify victims • paternity disputes • Process • Analyze DNA sections for repeats • Compare to individual of interest

  39. 3. DNA Fingerprinting (PCR) Step 4: Repeat with 2 strands of DNA.

  40. 4. Behavioral Genetics

  41. 4. Behavioral Genetics Is your personality defined by your genetic makeup? Study by knocking out genes. Three Assumptions: 1. You can quantify behavioral functions. Extroversion, Neuroticism, Conscientiousness, Agreeableness, & Openness 2. You can identify environmental factors. 3. You can do genetic tests to tell you about the person.

  42. 5. Genetic Engineering

  43. Genetic Engineering • Genetic engineering • Foreign genes inserted • Existing genes altered • Technique • Restriction enzymes cut DNA • Another DNA strand binds • New gene is expressed • Examples • Insulin • Agriculture • “knockout” mice • Bioterrorism

  44. Stem Cells, Cloning, and Regenerative Medicine • First cells can be anything • Later cells differentiate • Gene Control • Genes may turn on or off • Some genes are blocked • Stem Cell Line • Reproduce without differentiation

  45. 6. Gene Therapy

  46. 6. Gene Therapy Gene therapy Replace defective gene with healthy gene In vivo In vitro Problems Genes are inserted randomly Often no proteins are made Therapeutic viruses

  47. 6. Gene Therapy

  48. 7. Cancer

  49. Cancer-A Different Kind of Genetic Disease • Normal cell division is controlled • Cancer cells reproduce without restraint • Due to genetic defect • Usually 5-6 damaged genes • Collection of diseases • Genetic defects • Increase cancer probability • Lifetime risk >80% • Cure • Surgery, radiation, chemotherapy • Gene therapy

  50. 7. Cancer • P53 gene (and process) Defective gene Gene therapy

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