Term
| Describe the levels at which gene expressions is regulated in prokaryotes |
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Definition
1. Transcription - DNA
2. RNA processing - RNA
3. RNA stability - mRNA
4. Translation - protein
5. Post-translational- function performed by protein |
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Term
Describe the following genes
1. Housekeeping
2. Regulated
3. Induced
4. Repressed
5. Regulator |
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Definition
1. always turned on (rRNAs, tRNAs, structural proteins)
2. usually have specific function (growth, defense)
3. normally off but can turn on when needed
-catabolism
-turns on when food is present (lac operon)
4. normally high but can be turned off
-anabolism
-maintaining growth (tryptophan)
5. control expression of inducers and repressors |
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Term
| Describe Positive Control of Gene Regulation |
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Definition
-regulator gene product is called an activator
-bind to regulator protein binding sites and INCREASE transcriptional output
-influenced by effector molecules ->from environment
ex. inducers- inactive->activated trxn
ex. corepressors- active -> inactive (decreases trxn)
Changes can be
1. induced fit
2. translocation- place protein into nucleus so it can bind to DNA
3. sequestration- release inhibitory protein so activator can bind to DNA |
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Term
| Describe Negative Control of Gene Regulation |
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Definition
-regular gene product called repressor
-bind to regulator protein binding sites and DECREASE transcriptional output
-influenced by effector molecules-> from environment
inducer- de-repressed
corepressor- repressed |
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Term
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Definition
promoter+operator+gene
-genes with related functions that are grouped in a unit
-regulated by repressor gene that binds to operator and prevents polymerase from binding and transcribing |
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Term
Describe the Lac Operon
1. Classification
2. Repressor
3. Inducer
4. Glucose
5. cAMP |
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Definition
1. Negatively controlled induced operon-derepressed
2. LacI gene (binds to OPERATOR and allows polymerase to bind)
3. Allolactose- bind to LacI protein repressor
-changes shape of protein and it falls off
-polymerase can come in and transcribe
4. Glucose effect- when glucose is present, lac operon stays off
-inhibits adenylcyclases->> makes cAMP
5. inducer of lac operon- binds to catabolite activator protein (CAP-binds to PROMOTER and activates gene)
Glucose high- low cAMP > no trxn
Glucose low- high cAMP > trxn |
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Term
Describe the Tryp Operon- Negative Control
1. Classification
2. Repressor
3. Corepressor |
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Definition
1. negative control of repressed system
2. TrypR
3. Tryptophan
-binds to TrypR and stops polymerase from binding, stopping transcription |
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Term
Describe the Tryp Operon- Attenuation
1. Discovery
2. Binding Regions
3. Summary |
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Definition
1. deleted TrypR and there was still repression
2. Region 3 and 4 can bind leading to hairpin - ending transcription of gene
-Region 2 and 3 can bind, preventing hairpin
3. Without tryp, polymerase will stall at trpL peptide
-2 can then bind to 3, preventing hairpin
-polymerase can bind and continue to trxn
-with excess tryp, polymerase will finish trypL
-3 and 4 will bind, creating hairpin, ending trxn and preventing more tryp from being produced |
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Term
| Describe Temporal Control of Gene Expression |
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Definition
SP01 Bacteriophage -> B. subtilis
-early genes transcribed by host
-middle genes turn off early
-other genes turn off middle and turn on late |
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Term
| Describe Translation Control of Gene Expression |
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Definition
-stop mRNA from being turned into protein
-mRNA can be degraded or wait around until ready to be translated
*allows for more specific stopping point and more control |
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Term
| Describe Translation Control in E. coli |
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Definition
-ribosomal proteins need to be equal to amount of rRNA
1. S10 transcript- ribosomal protein that can build up in excess
2. L4 is protein that can build up and stop translation
-binds to 5' end of mRNA and inhibits translation
-as it builds up, ribosomal proteins will stop being produced
-when it slows down, it will bind to rRNA and continue |
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Term
| Describe Post Translational Control- Feedback Inhibition |
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Definition
| -occurs when product of pathway binds inhibits activity of first enzyme in the pathway |
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