1. Homework #2 is due 10/17 Bonus #1 is due 10/24 Exam key is online Office hours: M 10/8 10-11:30am 2-5pm in Bio 6

2. Fig 16.1 Gene Expression is controlled at all of these steps: DNA packaging Transcription RNA processing and transport RNA degradation Translation Post-translational

3. Eukaryotic transcription must be activated by binding of transcription factors

4. Enhancers are regulatory regions located some distance away from the promoter

5. Proteins that help bend DNA can play an important role in transcription Fig 11.14

6. DNA bends to bring different areas in to close contact.

7. Enhancer-blocking insulators prevent enhancer activation Fig 11.17

8. Fig 11.18 Insulators block the folding of DNA preventing enhancers from interacting with the promoter

9. How do eukaryotic cells jointly express several proteins (without operons)?

10. Promoter sequences where transcription factors can bind activating multiple gene in response to the environment

11. Fig 11.16 Combinations of regulatory transcription factors regulate expression of different genes

12. Promoters typically have several regulatory sequences

13. Steroid response element

14. Steroids bind to receptors/transcription factors inside cell get translocated to the nucleus bind to promoters and activate transcription. cytoplasm

15. Steroid response element

16. Fig 16.1 Gene Expression is controlled at all of these steps: DNA packaging Transcription RNA processing and transport RNA degradation Translation Post-translational

17. Fig 12.23 Alternate Splicing in Drosophila sex determination

18. Fig 12.23 Alternate splicing leads to sex determination in fruit flies

19. Mammalian mRNA Splice-Isoform Selection Is Tightly Controlled Jennifer L. Chisa and David T. Burke Genetics, Vol. 175: 1079-1087, March 2007 Regulation of gene expression is often in response to a changing environment. But how stable can alternative splicing be, and does it play a role in maintaining homeostasis?

20. Alternative splicing modifies at least half of all primary mRNA transcripts in mammals. More than one alternative splice isoform can be maintained concurrently in the steady state mRNA pool of a single tissue or cell type, and changes in the ratios of isoforms have been associated with physiological variation and susceptibility to disease. Splice isoforms with opposing functions can be generated; for example, different isoforms of Bcl-x have pro-apoptotic and anti-apoptotic function. Chisa, J. L. et al. Genetics 2007;175:1079-1087 Fig. 1

21. Using RT-PCR alternatively spliced versions of different genes were identified

22. Chisa, J. L. et al. Genetics 2007;175:1079-1087 Fig. 4 variation in splice-isoform ratios is conserved in two genetically diverse mouse populations Black= genetically heterogeneous population UMHET3 Red= a population of hybrid females

23. Chisa, J. L. et al. Genetics 2007;175:1079-1087 Fig. 5 In different individuals splice isoforms in different tissues are conserved

24. Chisa, J. L. et al. Genetics 2007;175:1079-1087 Fig. 6 Splice-isoform ratios differ between young and old animals (different environments)

25. Conclusions: Differences are observed in different tissues and at different ages, but there was always tight control of the relative amounts of the different splice-isoforms. Slight differences in alternative splicing may be indicative of abnormalities (disease).