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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition Solomon Berg Martin Chapter 13 Gene Regulation.

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Presentation on theme: "Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition Solomon Berg Martin Chapter 13 Gene Regulation."— Presentation transcript:

1 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition Solomon Berg Martin Chapter 13 Gene Regulation

2 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Gene regulation in bacteria and eukaryotes Bacterial cells –Grow rapidly and have short life span –Transcriptional-level control best Eukaryote cells –Long life span –Gene regulation complex –Transcriptional-level control dominates, but other levels important, also

3 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Gene regulation in bacteria Most organized into operons –Gene complex plus linked DNA –Each has single promoter region upstream Operator regulates transcriptional-level control of operon –When repressor protein binds to operator, it prevents transcription –Binds specifically to the lac operator sequence

4 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation The lac operon

5 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Genetic and biochemical characterization of the lac operon

6 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Inducible, repressible, and constitutive genes Inducible operon, such as lac operon, normally turned off Repressible operon, such as the trp operon, normally turned on Constitutive genes –Neither inducible nor repressible –Active at all times

7 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation The trp operon

8 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Negative regulators inhibit transcription Repressible and inducible operons When repressor protein binds to the operator, transcription is turned off Positive regulators stimulate transcription Some inducible operons Regulated by activator proteins

9 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Positive control of the lac operon

10 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation

11 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation A regulon

12 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Gene regulation in eukaryotic cells Not organized into operons Gene regulation occurs at the levels of –Transcription –mRNA processing –Translation –The protein product

13 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation

14 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Eukaryotic promoters vary in efficiency, depending on UPEs Promoter consists of –RNA polymerase-binding site –Upstream promoter elements (UPEs) Number and types of UPEs determine efficiency Inducible eukaryotic genes controlled by enhancers

15 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Regulation of transcription in eukaryotes

16 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Regulatory proteins

17 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Stimulation of transcription by an enhancer

18 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Chromosome organization may affect gene expression Genes are inactivated by changes in chromosome structure DNA methylation is mechanism that perpetuates gene inactivation Multiple copies of some genes present in one chromosome Gene amplification

19 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Differential mRNA processing Cells in each tissue produce own version of mRNA For example, different forms of troponin, a protein that regulates muscle contraction, produced in different muscle tissue

20 Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 13 Gene Regulation Differential mRNA processing


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