Homework #2 is due 10/17 Bonus #1 is due 10/24 Exam key is online

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

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

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

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 andactivate transcription. cytoplasm

15. Steroid response element

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

17. Alternate Splicing in Drosophila sex determination Fig 12.23

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

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 Chisa, J. L. et al. Genetics 2007;175:1079-1087 Fig. 1

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

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

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

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).