1. Big Idea 3- Part C Gene Regulation

2. Regulation of metabolic pathways

3. Operon Operon: cluster of related genes with on/off switch Three Parts: 1.Promoter – where RNA polymerase attaches 2.Operator – “on/off”, controls access of RNA poly 3.Genes – code for related enzymes in a pathway Bacterial control of gene expression

4. Regulatory generepressor Regulatory gene: produces repressor protein that binds to operator to block RNA poly

5. Repressible Operon (ON  OFF)

6. Repressible Operon  Normally ON  Anabolic (build organic molecules)  Organic molecule product acts as corepressor  binds to repressor to activate it  Operon is turned OFF trp operon  Eg. trp operon

7. trp operon

8. Inducible Operon  Normally OFF  Catabolic (break down food for energy) inducer  Repressor is active  inducer binds to and inactivates repressor  Operon is turned ON lac operon  Eg. lac operon

9. lac operon

10. 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 differential gene expression Differences between cell types is due to differential gene expression

11. Eukaryotic gene expression regulated at different stages

12. 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

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

15. Transcription Initiation Complex Enhancer promoter activators Enhancer regions bound to promoter region by activators

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

21. 1.Cell Division: large # identical cells through mitosis 2.Cell Differentiation: cells become specialized in structure & function 3.Morphogenesis: “creation of form” – organism’s shape Embryonic Development: Zygote  Organism

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

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

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

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

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

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

29. 1.Proto-oncogene = stimulates cell division 2.Tumor-suppressor gene = inhibits cell division Mutations in these genes can lead to cancer Control of Cell Cycle:

30. Proto-oncogene  Oncogene

31. 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

32. 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

33. Bacteria vs. Viruses BacteriaVirus Prokaryotic cell Most are free-living (some parasitic) Relatively large size Antibiotics used to kill bacteria Not a living cell (genes packaged in protein shell) Intracellular parasite 1/1000 size of bacteria Vaccines used to prevent viral infection Antiviral treatment

34. Viruses Very small (<ribosomes) Components = nucleic acid + capsid – Nucleic acid: DNA or RNA (double or single- stranded) – Capsid: protein shell – Some viruses also have viral envelopes that surround capsid Limited host range (eg. human cold virus infects upper respiratory tract) Reproduce within host cells

38. Simplified viral replicative cycle

39. Bacteriophage Virus that infects bacterial cells

40. Lytic Cycle of T4 Phage

41. Bacteriophage Reproduction Lytic Cycle: Lytic Cycle: – Use host machinery to make copies of virus lysis – Death of host cell by rupturing it (lysis) – Virulent phages replicate by this method Lysogenic Cycle: Lysogenic Cycle: – Phage DNA incorporated into host DNA and replicated along with it prophage – Phage DNA = prophage Temperate Phage: uses both methods of replication

42. Lytic Cycle vs. Lysogenic Cycle

43. Animal viruses have a membranous envelope Host membrane forms around exiting virus Difficult for host immune system to detect virus

44. Retrovirus reverse transcriptase RNA virus that uses reverse transcriptase (RNA  DNA) Newly made viral DNA inserted into chromosome of host provirus Host transcribes viral DNA (= provirus) to make new virus parts Example: HIV (Human Immunodeficiency Virus) Example: HIV (Human Immunodeficiency Virus)

45. HIV = Retrovirus

46. HIV ◦ Infects white blood cells ◦ HIV+: provirus (DNA inserted) ◦ AIDS: active viral reproduction

47. Vaccines Weakened virus or part of pathogen that triggers immune system response

48. Emerging viruses = mutation of existing viruses

49. Viroids Small, circular RNA molecules that infect plants Cause errors in regulatory systems that control plant growth Eg. coconut palms in Philippines

50. Prions Misfolded, infectious proteins that cause misfolding of normal proteins Eg. mad cow disease (BSE),Creutzfeldt-Jakob disease (humans), scrapie (sheep)

51. Diseases caused by prions Prions act slowly – incubation period of at least 10 years before symptoms develop Prions are virtually indestructible (cannot be denatured by heating) No known cure for prion diseases