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MircoBio Exam 3
Gene Expression
| Question | Answer |
|---|---|
| operon | cluster of bcterial genes along with an adjacent promoter that controls the transcription of those genes |
| operator | stretch of DNA that partially or completely overlaps the promoter and transcription start site |
| reason gene expression must be minimized | proteins synthesis is energy intensive |
| LacZ | beta galactosidase |
| LacY | lactose permease |
| LacA | thiogalacctoside transacetylase |
| 3 enzymes of lac operon | LacZ, LacY, LacA |
| function of beta galactosidase | cleaves lactose into glucose and galactose |
| function fo lactose permease | transports lactose across the cell membrane |
| function of transacetylase | unknown function |
| LacI gene makes | LacI DNA-binding protein - REPRESSOR |
| LacI: on or off? | always on at a very low level |
| LacI protein does what? | binds the OPERATOR of the lac operon |
| what disables DNA-binding affinity of LacI repressor protein? | allolactose bound to LacI |
| lactose is converted to _____ in equillibrium | allolactose (an isomer) |
| what happens when allolactose is present in the cell? | binds to LacI, LacI loses DNA affinity, falls off OPERATOR, RNA pol can bind to PROMOTER, transcription can begin |
| RNA pol binds to | binds to promotor |
| repressor protein binds to | binds to operator |
| cell senses presence of lactose via | presence of allolactose |
| if glucose and lactose are present | cell will metabolize glucose preferentially |
| level of lac operon enzymes produced when glucose is present | very low level of lac operon enzyme production |
| level of lac operon enzymes produced when glucose is used up | medium level of lac operon enzyme production |
| level of lac operon enzyme production when cAMP levels are high | high level of lac operon enzyme production |
| high glucose levels = ____ cAMP levels | low cAMP levels (high ATP levels) |
| cAMP binds to | binds to CAP |
| CAP | Catabolite Activator Protein |
| CAP binds to | binds to special site on DNA |
| lac operon is under _____ control | under negative (LacI) and positive (CAP) control |
| negative control of Lac operon | LacI control |
| positive control of Lac operon | CAP control |
| Trp operon is usually | usually on |
| how many proteins in Trp operon? | 5 |
| how many enzymes produced by Trp operon? | 3 |
| which operon is inducible? | Lac operon |
| which operon is repressible | Trp operon |
| DNA binding protein for Trp control | Tryptophan repressor (trpR) |
| usual level of production of trpR | always (constitutively), at low levels |
| trpR is inactivated by | binding of tryptophan amino acid, then it loses DNA affinity |
| quorum sensing bacterial genes | luciferase, beta lactamase |
| bacteria that makes luciferase | vibrio fischeri |
| do vibrio fischeri living outside a squid produce luciferase? | no |
| molecule that allows quorum sensing in vibrio | VAI (Vibrio fischeri AutoInducer) |
| important property of VAI | diffuses in and out of cell |
| VAI binds to | LUX protein, activates, LUX protein, which then binds to DNA at LuxO site |
| Lux protein is bound by ___ | VAI |
| Lux protein binds to ___ | LuxO site |
| what increases RNA pol to promoter of Lux Operon | binding of Lux protein to LuxO site |
| Trp is inhibited by | binding of trpR to operator |
Created by:
epiphenom
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