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Review Warm-Up

Review Warm-Up. What is the Central Dogma? How does prokaryotic DNA compare to eukaryotic DNA? How is DNA organized in eukaryotic cells?. Ch. 18 Warm-Up. Draw and label the 3 parts of an operon. Contrast inducible vs. repressible operons.

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Review Warm-Up

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  1. Review Warm-Up • What is the Central Dogma? • How does prokaryotic DNA compare to eukaryotic DNA? • How is DNA organized in eukaryotic cells?

  2. Ch. 18 Warm-Up • Draw and label the 3 parts of an operon. • Contrast inducible vs. repressible operons. • How does DNA methylation and histone acetylation affect gene expression?

  3. Ch. 18 Warm-Up • List and describe the 3 processes that are involved in transforming a zygote. • Compare oncogenes, proto-oncogenes, and tumor suppresor genes. • What are the roles of the ras gene and the p53 gene?

  4. Regulation of Gene Expression Chapter 18

  5. Regulation of Gene Expression by Bacteria Transcription

  6. Regulation of metabolic pathways

  7. Bacterial control of gene expression Operon: cluster of related genes with on/off switch Three Parts: • Promoter – where RNA polymerase attaches • Operator – “on/off”, controls access of RNA poly • Genes – code for related enzymes in a pathway

  8. Regulatory gene: produces repressorprotein that binds to operator to block RNA poly

  9. Repressible Operon (ON  OFF) Inducible Operon (OFF  ON)

  10. Repressible Operon • Normally ON • Anabolic (build organic molecules) • Organic molecule product acts as corepressor binds to repressor to activate it • Operon is turned OFF • Eg. trpoperon

  11. trp operon

  12. Inducible Operon • Normally OFF • Catabolic (break down food for energy) • Repressor is active inducerbinds to and inactivates repressor • Operon is turned ON • Eg. lacoperon

  13. lac operon

  14. Regulation of Gene Expression by Eukaryotes Many stages

  15. Typical human cell: only 20% of genes expressed at any given time • Different cell types (with identical genomes) turn on different genes to carry out specific functions • Differences between cell types is due to differential gene expression

  16. Eukaryotic gene expression regulated at different stages

  17. Chromatin Structure: • Tightly bound DNA less accessible for transcription • DNA methylation: methyl groups added to DNA; tightly packed;  transcription • Histone acetylation: acetyl groups added to histones; loosened;  transcription

  18. Epigenetic Inheritance • Modifications on chromatin can be passed on to future generations • Unlike DNA mutations, these changes to chromatin can be reversed (de-methylation of DNA) • Explains differences between identical twins

  19. Transcription Initiation: • Control elements bind transcription factors • Enhances gene expression

  20. Transcription Initiation Complex Enhancerregions bound to promoter region by activators

  21. Regulation of mRNA: • micro RNAs (miRNAs) and small interfering RNAs (siRNAs) can bind to mRNA and degrade it or block translation

  22. Summary of Eukaryotic Gene Expression

  23. Embryonic Development of Multicellular Organisms Section 18.4

  24. Embryonic Development:Zygote  Organism • Cell Division: large # identical cells through mitosis • Cell Differentiation: cells become specialized in structure & function • Morphogenesis: “creation of form” – organism’s shape

  25. Determination: irreversible series of events that lead to cell differentiation

  26. Cytoplasmic determinants: maternal substances in egg distributed unevenly in early cells of embryo

  27. Induction: cells triggered to differentiate • Cell-Cell Signals: molecules produced by one cell influences neighboring cells • Eg. Growth factors

  28. Pattern formation: setting up the body plan (head, tail, L/R, back, front)

  29. Morphogens: substances that establish an embryo’s axes

  30. Homeotic genes: master control genes that control pattern formation (eg. Hox genes)

  31. Cancer results from genetic changes that affect cell cycle control Section 18.5

  32. Control of Cell Cycle: • Proto-oncogene = stimulates cell division • Tumor-suppressor gene = inhibits cell division • Mutations in these genes can lead to cancer

  33. Gene that stimulates normal cell growth & division • Mutation in proto-oncogene • Cancer-causing gene Effects: • Increase productof proto-oncogene • Increase activityof each protein molecule produced by gene Proto-Oncogene Oncogene

  34. Proto-oncogene  Oncogene

  35. Genes involved in cancer: • Ras gene: stimulates cell cycle (proto-oncogene) • Mutations of ras occurs in 30% of cancers • p53 gene: tumor-suppresor gene • Functions: halt cell cycle for DNA repair, turn on DNA repair, activate apoptosis (cell death) • Mutations of p53 in 50+% of cancers

  36. Cancer results when mutations accumulate (5-7 changes in DNA) • Active oncogenes + loss of tumor-suppressor genes • The longer we live, the more likely that cancer might develop

  37. Summary • Embryonic development occurs when gene regulation proceeds correctly • Cancer occurs when gene regulation goes awry

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