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Chapter 12 How Genes Work

Chapter 12 How Genes Work. Cooperative Activity. 1. What do you know about DNA? 2. What do you want to know about DNA?. DNA & Today. 1988: DNA profiling was used in Britain, murder of 2 girls 1994: OJ Simpson murder trial Crime shows Cold Cases. Review: What is DNA?.

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Chapter 12 How Genes Work

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  1. Chapter 12 How Genes Work

  2. Cooperative Activity 1. What do you know about DNA? 2. What do you want to know about DNA?

  3. DNA & Today • 1988: DNA profiling was used in Britain, murder of 2 girls • 1994: OJ Simpson murder trial • Crime shows • Cold Cases

  4. Review: What is DNA? • DNA stores our genetic information • Where is DNA found? • Nucleus of cell

  5. What is a gene? • Section of DNA that codes for a trait • Where are genes found? • Chromosomes

  6. What is a chromosome? • Bundles of DNA • Where are chromosomes found? • Nucleus of cell

  7. What do these words have in common? • DNA • Chromosomes • Genes

  8. Introduction • Humans are made up of: • 20,000 – 30,000 genes • 23 pairs of chromosomes • 3 billion nitrogen bases

  9. Human Genome • Genetic map of the human body • Includes chromosomes and genes

  10. Human Genome (cont.) • You inherit 2 copies of every gene • one from mom & one from dad

  11. Human Genome (cont.) • Only 1% of your DNA codes for genes

  12. Human Genome (cont.)

  13. Why are genes important? • Genes contain the instructions to make proteins

  14. Structure of DNA • Made up of parts: nucleotides • Chemical building blocks

  15. Parts of a Nucleotide • Nitrogen-containing Base (A, T, C, G) • Sugar (Deoxyribose) • Phosphate Group

  16. Base Pairing • Adenine (A) & Thymine (T) • Cytosine (C) & Guanine (G) • Hydrogen bonds hold bases together

  17. Base Pairing

  18. DNA – Basic Structure • Backbone: Alternating Sugar & Phosphate • Inside: Nitrogen Bases • Shape: Double Helix

  19. Structure of DNA

  20. Making Copies of DNA • Every time our body makes new cells, we need more DNA • This process is called: DNA Replication

  21. DNA Replication – Step 1 Helicase (enzyme) • unwinds chains • separates nucleotides by breaking bonds

  22. DNA Replication – Step 2 2. DNA polymerase assembles new chains • Complementary to one another

  23. DNA Replication – Step 3 3. DNA ligase links the two sections

  24. DNA Replication – End Result Two identical strands of DNA (Two daughterDNA)

  25. Reading the Genetic Code • Genes have the instructions to make proteins • Occurs in two steps • Transcription • Translation

  26. Review: Protein Synthesis • Q: Which organelle helps make proteins? • Ans: Ribosomes

  27. Transcription • Process of copying genetic information from DNA to mRNA (messenger) • Takes place in nucleus

  28. Why do we need mRNA? Carries copied info from nucleus to ribosomes DNA cannot leave the nucleus Protect the code

  29. Transcription Steps RNA Polymerase 1. Unwinds DNA double helix 2. Adds RNA nucleotides to build mRNA chain

  30. Transcription Steps (cont.) 3. mRNA moves out of nucleus

  31. Transcription Animation

  32. Translation • Process of assembling amino acids into proteins on ribosomes • Order of amino acid determines protein

  33. Translation Steps 1.) 3 letter code on tRNA anticodonmatches up with mRNA codon • tRNA (transfer)

  34. Translation Steps (cont) 2.)tRNA interprets the mRNA code sequence 3.)Code is read 3 letters at a time

  35. Translation Steps (cont) 4.)Amino acids bond together to form proteins

  36. Mutations • A change in the copying of the genetic message • Can occur during DNA replication or transcription • Rare - occur in 1 out of 1 billion bases

  37. Factors that affect the rate of mutations • Mutagens • Radiation / UV light • Chemicals

  38. Translating The Code Example • tRNA anticodon: AAA • mRNA codon: UUU • UUU codes for amino acid phenylalanine

  39. Translation mRNA tRNA

  40. Translation

  41. Codon (mRNA) Table

  42. RNA ribonucleic acid Structure A – U (Uracil) C – G Single stranded DNA deoxyribo- nucleic acid Structure A – T C – G Double stranded Venn Diagram: RNA & DNA

  43. MCAS Questions Which of the following statements best describes why the change in only one DNA base of the hemoglobin gene results in a different protein product of the gene? A. The change prevents mRNA from being made.  B. The change alters the amino acid sequence of the protein.  C. The change causes the blood cells to divide in an uncontrolled way.  D. The change creates a second strand of mRNA for each RNA molecule.

  44. MCAS Questions In a eukaryotic cell, which of the following processes directly involves DNA? A. translation  B. cellular respiration  C. active transport of ions D. replication of chromosomes

  45. MCAS Questions In a molecule of double-stranded DNA, the amount of adenine present is always equal to the amount of A. cytosine.  C. thymine. B. guanine.   D. uracil.

  46. MCAS Questions During DNA replication, the wrong nucleotide was inserted in the DNA sequence. Which of the following terms describes this situation? A. mutation  C. transcription B. regeneration   D. translation

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