Gene Regulation II. Genetics Bio 36404

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Francis Underwood
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1 Gene Regulation II Genetics Bio 36404

2 Review DNA RNA protein Every cell in body has same DNA. Not all cells make all proteins What turns genes on and off?

3 Prokaryotes Operon - group of related genes and their regulatory regions Promoter Operator gene A gene B gene C

4 Types of Control constitutive - cell makes protein regardless of environment e.g. respiration enzymes inducible - gene for protein turned on by environmental signal. repressible - gene for protein turned off by an environmental signal

5 Lac Operon Gene group involved in processing lactose lac i! RNA Polymerase Promoter Operator Lac z Lac y Lac a mrna repressor protein P TA BG- ß-galactosidase digests lactose permease transports lactose into cell transacetylase removes byproducts?

6 No Lactose in Environment lac i! RNA Promoter Polymerase Operator Lac z Lac y Lac a Repressor binds to O RNA Polymerase blocked No transcription No enzymes made Negative Control

7 Lactose in Environment inducible or repressible? lac i Promoter Operator Lac z Lac y Lac a lactose pulls repressor from operator transcription and translation occur BG- P TA

8 Lac Operon - Positive Control CAP lac i Promoter! camp Operator Lac z Lac y Lac a camp-cap binds to Promoter Increases transcription when glucose is low BG- P TA!8

9 Tryptophan (trp) amino acid H H O H N C CH2 C O H N H

10 Tryptophan Synthesis precursor int 1 int 2 int 3 int 4 trp Enz A Enz B Enz C Enz D Enz E!10

11 Tryptophan Synthesis precursor int 1 int 2 int 3 int 4 trp Enz A Enz B Enz C Enz D Enz E!10

12 Trp Operon Gene group involved in synthesis of tryptophan DNA trp r P O trpe trpd trpc trpb trpa

13 Trp Operon Gene group involved in synthesis of tryptophan DNA trp r P O trpe trpd trpc trpb trpa Polycistronic RNA

14 Trp Operon Gene group involved in synthesis of tryptophan DNA trp r P O trpe trpd trpc trpb trpa Polycistronic RNA Enz. E Enz. D Enz. C Enz. B Enz. A

15 Trp Operon Gene group involved in synthesis of tryptophan DNA trp r P O trpe trpd trpc trpb trpa Polycistronic RNA inactive repressor Enz. E Enz. D Enz. C Enz. B Enz. A

16 No Trp in Environment trp r P O trpe trpd trpc trpb trpa inactive repressor

17 No Trp in Environment! RNA trp r Polymerase P O trpe trpd trpc trpb trpa inactive repressor

18 No Trp in Environment Repressor cannot bind to O Transcription/Translation occur trp r P O trpe trpd trpc trpb trpa inactive repressor Enz. E Enz. D Enz. C Enz. B Enz. A

19 Tryptophan in Environment trp r P O trpe trpd trpc trpb trpa inactive repressor tryptophan!13

20 Tryptophan in Environment trp r P O trpe trpd trpc trpb trpa active repressor Trp Activates Repressor tryptophan!13

21 Tryptophan in Environment trp r P O trpe trpd trpc trpb trpa active repressor Trp Activates Repressor Repressor binds to O tryptophan!13

22 Tryptophan in Environment! RNA Polymerase trp r P O trpe trpd trpc trpb trpa active repressor Trp Activates Repressor Repressor binds to O Polymerase blocked - no transcription tryptophan!13

23 Transcription/Translation Simultaneous DNA trp E trp D trp C trp B trp A Prokaryotes - no nucleus Transcription mrna Translation

24 Attenuation Additional level of control involving both transcription and translation trp r P O L trpe trpd trpc trpb trpa DNA Leader - L base pairs next to trp E transcribed as part of mrna

25 Attenuation Additional level of control involving both transcription and translation DNA trp r P O L trpe trpd trpc trpb trpa L mrna trpe trpd trpc trpb trpa Leader - L base pairs next to trp E transcribed as part of mrna

26 Leader Region mrna leader as 4 domains: 1, 2, 3, 4 Domain 1 has several codons for trp Domain 3 can loosely pair with 2 or 4

27 Leader Region (mrna) Low trp in env. Translation of 1 slow 2-3 loop forms transcription continues High trp in env. Translation of 1 fast 3-4 termination hairpin forms inhibits further transcription

28 Activity Review Trp Operon Effect of mutation on function!18

Sparing dystrophic muscle

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