1. Introduction to Genetic Analysis
Griffiths • Wessler • Carroll • Doebley
Introduction to
Genetic Analysis
ELEVENTH EDITION
CHAPTER 12
Regulation of Gene Expression
in Eukaryotes
© 2015 W. H. Freeman and Company

2. CHAPTER OUTLINE
12.1 Transcriptional regulation in eukaryotes: an overview
12.2 Lessons from yeast: the GAL system
12.3 Dynamic chromatin
12.4 Activation of genes in a chromatin environment
12.5 Long-term inactivation of genes in a chromatin environment
12.6 Gender-specific silencing of genes and whole chromosomes
12.7 Post-transcriptional gene repression by miRNAs

3. Overview of transcriptional regulation in Prokaryotes and Eukaryotes

4. Question
Which of the following statements best describes the ground state for expression of genes in eukaryotic cells?
Gene expression is “on” unless specifically inhibited by the binding of repressor proteins.
Gene expression is “off” unless specifically turned on by the binding of transcriptional activator proteins.
Gene expression is constitutively “on” in heterochromatin but is constitutively “off” in euchromatin.
Gene expression is constitutively “off” in heterochromatin but is constitutively “on” in euchromatin.

5. Promoter-proximal elements precede the promoter of a eukaryotic gene

6. The Gal pathway

7. Yeast

8. Transcriptional activator proteins bind to UAS elements in yeast

9. Transcriptional activator proteins are modular

10. Transcriptional activator proteins may be activated by an inducer

11. Transcriptional activator proteins recruit the transcriptional machinery

12. Question
Which of the following is likely to be a functional domain of a transcription factor that activates the expression of specific genes only under the appropriate environmental cues?
DNA-binding domain
Transcriptional activation domain
RNA synthesis domain
All of the above
a and b

13. The structure of chromatin

14. Chromatin remodeling exposes regulatory sequences
SWI/SNF-nudges nucleosomes

15. Modifications of histone tails by acetylation (A) and methylation (M): histone code

16. Page 446: HAT-Histone acetyltransferases and HDACs-Histone deacetylases

17. Acetylation of histone tails results in altered chromatin and affect gene expression
Hypoacetylated-inactive gene
Hyperacetylation-active gene

18. Histone deacetylation can turn off gene transcription

19. Page 448: HMTase-Histone methyltransferase; histone methylation associated with inactive genes

20. Inheritance of chromatin states

21. Page 449

22. A model for the inheritance of DNA methylation

23. Enhanceosomes help recruit the transcriptional machinery

24. Enhanceosomes recruit chromatin remodelers

25. Enhancer-blocking insulators prevent enhancer activation

26. Model for how enhancer-blocking insulators might work

27. Question An enhancer is best described as a:
Specialized DNA sequence that acts to promote expression of specific genes
Transcription factor that acts to promote expression of specific genes
Binding site for RNA polymerase
Protein that binds to RNA polymerase, thereby modulating the rate at which RNA polymerase transcribes a given gene
TATA box-containing DNA element

28. Spreading heterochromatin can silence genes

29. Barrier insulators stop the spread of heterochromatin

30. Epigenetics
Epigenetics-the study of heritable changes in gene function that do not involve changes in the DNA sequence; literally, over or above traditional genetics
Epigenetic changes or “marks” include:
Histone acetylation- associated with gene activity
Histone methylation- associated with gene inactivity
DNA methylation- associated with gene inactivity
These epigenetic marks are added by chemicals in your environment (even in utero) and by your behavior (e.g., smoking, diet) and are passed onto your offspring!
Specific epigenetic processes include imprinting, gene silencing, X chromosome inactivation, and position effects.

31. Epigenetics

32. Genomic imprinting requires insulators Maternal imprinting = mother’s allele is inactive Paternal imprinting = father’s allele is inactive

33. Unusual inheritance of imprinted genes

34. A model for X-chromosome inactivation

35. Possible models for the repression of translation by miRNA