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The control of gene expression enable individual bacteria to adjust their

The control of gene expression enable individual bacteria to adjust their metabolism to environmental change. Regulation of a Metabolic Pathway. Operon : consists of a closely related group of genes that act together and code for the enzymes that control a particular

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The control of gene expression enable individual bacteria to adjust their

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  1. The control of gene expression enable individual bacteria to adjust their metabolism to environmental change

  2. Regulation of a Metabolic Pathway

  3. Operon : consists of a closely related group of genes that act together and code for the enzymes that control a particular metabolic pathway; con- sists of an operator, pro- moter, and the genes they control

  4. The trp operon: regulated synthesis of repressible enzymes

  5. The trp operon: regulated synthesis of repressible enzymes

  6. The “switch” for turning the genes off and on is called an operator. It is positioned within the pro- moter or between the pro- moter and enzyme-encoding genes, controlling access to the genes.

  7. What determines if the operator is on? By itself, it is on – RNA polymerase can bind to the promoter. It can be switched off by a protein called a repressor.

  8. The trp operon: regulated synthesis of repressible enzymes

  9. The repressor is a product of a regulatory gene. These are transcribed continuously, although at a low rate.

  10. Tryptophan (trp) is synthe- sized from E. coli from a pre- cursor molecule in a series of steps. The trp operon is said to be a repressible operon because transcription of it is inhibited when a specific small molecule (tryptophan) binds to a regulatory protein

  11. The lac operon: regulated synthesis of inducible enzymes

  12. The lac operon: regulated synthesis of inducible enzymes

  13. In contrast, an inducible operon, like the lac operon, is stimulated (i.e. induced) when a specific small molecule interacts with a regulatory protein.

  14. The disaccharide, lactose, is available to E. coli if the human host drinks milk. The bacteria can absorb the lactose and break it down for energy. Lactose metabolism begins with the hydrolysis of lactose into its two monosaccharides

  15. The gene for beta galactosidase is part of an operon, the lac operon, that includes two other genes coding for proteins that function in lactose metabolism

  16. The enzyme that catalyzes this reaction is called beta galactosidase. In the presence of lactose it can increase 1000x in 15 min.

  17. Positive control: cAMP receptor protein CAP CAP

  18. Positive control: cAMP receptor protein CAP CAP

  19. Lac Operon: http://highered.mheducation.com/sites/9834092339/student_view0/chapter15/the_lac_operon.html http://www.sumanasinc.com/webcontent/animations/content/lacoperon.html Trp Operon: http://highered.mheducation.com/sites/0072995246/student_view0/chapter7/the_trp_operon.html The Operons: (Paul Andersen on Bozeman Science) http://www.bozemanscience.com/the-operon/ The Amoeba Sisters:  https://www.youtube.com/watch?v=h_1QLdtF8d0&list=PLwL0Myd7Dk1F0iQPGrjehze3eDpco1eVz&index=41&t=0s

  20. Which of the following is a protein produced by a regulatory gene? • operon • mRNA • promoter  • repressor  • corepressor

  21. The tryptophan operon is a repressible operon that is: • permanently turned on. • turned on only when tryptophan is present in the growth medium. • turned off only when glucose is present in the growth medium. • turned on only when glucose is present in the growth medium. • turned off whenever tryptophan is added to the growth medium

  22. Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation? • inducer  • promoter  • RNA polymerase • transcription factor  • cAMP

  23. For a repressible operon to be transcribed, which of the following must occur? • A corepressor must be present. • RNA polymerase and the repressor must • be active. • C) RNA polymerase must bind to the promoter, and the repressor must be inactive. • D) RNA polymerase cannot be present, and the repressor must be inactive. • E) RNA polymerase must not occupy the promoter, and the repressor must be inactive

  24. Transcription of the structural genes in an inducible operon: • occurs continuously in the cell. • starts when the pathway's regulatory gene is present. • starts when the pathway's substrate is present. • stops when the pathway's product is present. • does not result in the production of enzymes.

  25. The lactose operon is likely to be transcribed when: • there is more glucose in the cell than lactose. • the cyclic AMP levels are low. • there is glucose but no lactose in the cell. • the cyclic AMP and lactose levels are both high within the cell. • the cAMP level is high and the lactose level is low.

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