Good Morning!

1. Good Morning! • Turn in your mutations packet. • When your partner arrives – finish your lab activity from yesterday. • Due by 11:05

2. February 10, 2016 • HW: Finish Lac OperonPkt • Reminder: Test Tuesday Ch 16-18 • Agenda: • Finish Model • Chapter 18 Regulation • Trp and Lac • Chrome Books: Lac Operon

3. Regulation of Gene Expression Chapter 18

4. Regulation of Gene Expression by Bacteria Transcription

5. Bacteria respond to their environment • Natural selection has favored bacteria that can conserve resources and energy • E.Coli / Human Intestine • Obtains nutrients from the erratic eating habits of its host • Needs the amino acid tryptophan • Without it • Synthesize its own tryptophan • Host consumes a meal w/ tryptophan • Stop producing tryptophan

6. First Level of Metabolic Control Enzyme 1 is inhibited by the end product of the pathway. If Trp accumulates, it shuts down the synthesis of more Trp by inhibiting it Feedback Inhibition Operon Model

7. Second Level of Metabolic Control • Cells can adjust the production level of enzymes • By regulating the genes that code for those enzymes • If the gut has a lot of tryptophan • The cell stops making the enzymes that synthesize tryptophan • During transcription

8. Bacterial control of gene expression Operon: entire stretch of related genes required for enzyme production Three Parts: • Promoter – where RNA polymerase attaches • Operator – “on/off”, controls access of RNA poly to the genes • Genes – code for related enzymes in a pathway

9. The operon is always turned on. Unless….. A repressor is present.

10. Regulatory gene • Trp repressor is the protein product of a regulatory gene trpR, has its own promotor • Located upstream of the trp operon • Continuously transcribed at a low rate, inactive • Becomes active if it binds with tryptophan to change its shape • Tryptophan is called a co-repressor in this example

11. trpoperon Anabolic

12. Repressible and Inducible Operons • TrpOperon: Repressible: Usually on, but can be inhibited or repressed by a repressor Comparison • Lac Operon: Inducible: Usually off, but can be turned stimulated or induced when a molecule interacts with a regulatory protein

13. Lac Operon • E.Coli and Lactose (Dissacharride) • Lacl regulatory gene upstream of the promoter • The lac repressor is active alone. • Lactose act as an inducer • Binds to the repressor to inactivate it • Now the lacoperon can be transcribed

14. lacoperon catabolic

15. Gene Regulation:Positive vs. Negative Control • Negative control of genes: operons are switched offby active form of repressor protein • Eg. trp operon, lacoperon • Positive control of genes: regulatory protein interacts directly with genome to increasetranscription • Eg. cAMP& CAP

16. E.Coli, Glucose, Lactose • E.Coli prefers glucose over lactose • How does it sense the concentration of glucose and relay this to the lac operon? • Allosteric regulatory protein: CAMP • Accumulates when glucose is scarce

17. When glucose comes around… • Glucose levels high, CAMP Low, CAP Inactive • Decrease RNA Polymerase Affinity

18. What happens when glucose levels drop?

19. When glucose goes on vacation. • cAMP accumulates when glucose is scarce • cAMP binds to CAP (catabolite activator protein) • ↑ affinity of RNA polymerase • ↑ transcription • Start using lactose again. cAMP + CAP = Positive Control

20. Helpful Tips: PROG Promotor, Repressor, Operator, Genes

21. Lac Operon: Chrome Books

23. February 11, 2016 • HW: Honors Biology Test Practice • Agenda: • Chapter 17 Check for Understanding • Eukaryotic Gene Regulation • Epigenetics Video Clips

24. Regulation of Gene Expression by Eukaryotes Many stages

25. Eukaryotic Gene Regulation • Typical human cell: only 20% of genes expressed at any given time • Constantly switched on/off • Example: Cell Specialization • Different cell types (with identical genomes) turn on different genes to carry out specific functions • Differences between cell types is (not due to different genes) but is due to differential gene expression

26. Cell differentiation

27. Eukaryotic gene expression regulated at different stages.The boxes indicate the processes most often regulated.

28. Example: Regulation of Chromatin Structure: • Organization of chromatin and chemical modification to chromatin can influence gene expression

29. Acetyl and Methyl Modifications

30. Epigenetic Inheritance • Modifications on chromatin can be passed on to future generations • Changes gene expression, not the underlying DNA • Effects phenotype not genotype

31. Video: The Epigenome at a Glance Genetic Science Learning Center

32. Video: The Epigenetics of Identical Twins Genetic Science Learning Center

33. Epigenetics and Your Genome TED

34. Transcription Initiation: • Specific transcription factors (activators or repressors) bind to control elements (enhancer region) • Activators: increase transcription • Repressors: decrease transcription

35. Transcription Initiation Complex Activators bind to enhancer regions + other proteins + RNA polymerase

36. Cell type-specific transcription

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

38. Summary of Eukaryotic Gene Expression

42. I am after school until 2:15 today.