Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Control of Gene Expression More about bacteria! • Now part of the rest of the bacteria chromosome can be transferred to another bacteria cell: • Recombination exchanges segments of DNA. Why would a bacteria want to control gene expression anyway? In order to adjust to the changing environment. • For example: • Amino acid, Tryptophan (found in chicken, turkey, fish, soybeans, etc.) E. coli can make their own tryptophan, but are they going to bother making their own when Thanksgiving rolls around?! But first…some VOCABULARY! Operon The entire stretch of DNA required for enzyme production. Includes the operator, promoter and genes they control. Promoter Region where RNA polyermase binds Operator Acts as an “on-off switch” Region between the promoter and the first gene Repressor Protein that binds to the operator and blocks the attachment of RNA polymerase Corepressor A small molecule that cooperates with a repressor protein to switch an operator off Regulatory Gene The gene that produces repressors Inducer A molecule that inactivates the repressor Now let’s put it all together! How do all the parts interact? NO tryptophan in environment: • • • Repressor does not bind to the operator RNA polymerase attaches Enzymes are made that make tryptophan What happens if we just ate some turkey?! Tryptophan in the environment: • Tryptophan acts as a corepressor and binds to the repressor. • The repressor now has the correct shape to bind to the operator. • RNA polymerase can NOT attach to the promotor • Tryptophan synthesis is STOPPED! Repressible vs. Inducible Operons Repressible operon: one that is inhibited when a specific small molecule binds to a regulatory protein • Normally ON: active • Function in anabolic pathways (making) Inducible operon: one that is stimulated when a specific small molecule interacts with a regulatory protein. • Normally OFF: inactive • Function in catabolic pathways (breaking down) Inducible operon example… The lac operon contains genes that code for enzymes that break down lactose. • Your mom forgot to buy milk: your bacteria are not going to make any enzymes for the breakdown of lactose (OFF) No milk = operator OFF Got milk = operator ON Do you know your vocabulary?! Let’s find out! Clue #1 The entire stretch of DNA required for enzyme production. Includes the operator, promoter and genes they control. Operon Clue #2 Region where RNA polyermase binds Promoter Clue #3 Acts as an “on-off switch” Region between the promoter and the first gene Operator Clue #4 Protein that binds to the operator and blocks the attachment of RNA polymerase Repressor Clue #5 A small molecule that cooperates with a repressor protein to switch an operator off Corepressor Clue #6 The gene that produces repressors Regulatory Gene Clue #7 A molecule that inactivates the repressor Inducer