Term
| What are the three patterns of gene expression? |
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Definition
| Constitutive, Inducible, Repressible |
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Term
| What gene expression is associated with housekeeping genes, and is always expressed? |
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Definition
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Term
| What gene expression is off as default, but can be induced to turn on? |
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Definition
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Term
| What gene expression is always expressed but can be turned off? |
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Definition
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Term
| What genes are involved with degradative pathways? |
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Definition
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Term
| What genes are often involved with biosynthetic pathways? |
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Definition
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Term
| What is negative control? |
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Definition
| When a repressor binds to the control region of a gene and inhibits expression |
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Term
| What is positive control? |
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Definition
| When an activator protein binds to the control region of a gene, and activates expression |
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Term
| What regulates the binding of regulatory proteins to the control regions of genes? |
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Definition
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Term
| What effector molecule turns off gene expression in repressible systems? |
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Definition
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Term
| What gene expression pattern and control system operate the lac Operon? |
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Definition
| Inducible system (normally off, can be turned on), negative control (when a regulator binds, it inhibits expression) |
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Term
| What are the components of the lac Operon? |
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Definition
| Promoter, Operator, 3 protein-coding genes |
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Term
| Where does RNA polyermase bind in the lac Operon? |
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Definition
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Term
| Where does the lac repressor bind? |
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Definition
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Term
| What are the three protein-coding genes? |
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Definition
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Term
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Definition
| It is B-galactosidase; breaks down lactose, into galactose, glucose, and allolactose |
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Term
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Definition
| It is permease; it transports lactose into the cell |
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Term
| What gene encodes the lac repressor? |
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Definition
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Term
| True or false: lacI is synthesized inducibly? |
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Definition
| False; it is synthesized constitutively |
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Term
| If lactose is not present, what happens? |
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Definition
| lac repressor bind the operator; inhibits RNA polymerase; turns expression of the lac genes off |
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Term
| If lactose is present, what happens? |
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Definition
| The effector molecule binds to the lac repressor, which prevents it from binding to the operator; allows RNA polymerase to bind; gene expression is turned on |
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Term
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Definition
| Allolactose is the effector molecule that binds the repressor molecule, inhibiting it's binding to the operator |
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Term
| What would cause constitutive expression of the lac Operon? |
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Definition
| Mutations in the lacI gene (lacI-) or in the operator region (lacOc) |
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Term
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Definition
| A repressor which cannot bind to the lac Operator (here, the repressor is mutated) |
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Term
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Definition
| An operator which cannot bind the repressor (here, the operator is mutated) |
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Term
| What are partial diploids in the lac Operon? |
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Definition
| They are bacterial cells with a chromosomal lac Operon and a lac operon on an F' plasmid |
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Term
| True or False: In partial diploids, lacI can act in cis and trans |
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Definition
| True, it works back and forth between chromosomes |
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Term
| Why can the lacI act in cis and trans? |
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Definition
| The lac repressor protein is diffusible and binds to the operator of the chromosome, and the F' plasmid |
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Term
| Why can the lac operator (lacO) only act in cis? |
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Definition
| Because a functional operator must be near the promoter of the linked lac genes on the same DNA molecule |
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Term
| What catabolite represses the lac operon and how? |
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Definition
| Glucose, by inhibiting the enzyme adenylcyclase, which results in low levels of cAMP |
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Term
| What happens when glucose levels are low? |
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Definition
| cAMP levels are increased, and bind to the catabolite activator protein CAP |
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Term
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Definition
A positively acting regulator protein that binds to the control region of a gene when it is bound by the effector molecule cAMP
-a regulator, but it can only bind to the operator IF the effector is bound to it |
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Term
| When CAP-cAMP (regulator + effector) bind to the promoter, what happens? |
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Definition
| RNA polymerase is recruited which induces the lac Operon |
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Term
| True or False: CAP-cAMP mediates negative regulation of the lac operon |
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Definition
| False that shit, it mediates positive regulation |
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Term
| What gene expression and control system regulate the trp operon? |
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Definition
| A repressible system, under negative control |
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Term
| What happens if tryptophan is not present? |
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Definition
| The trp repressor can't bind to the operator, so RNA polymerase binds to the promoter, and the operon is expressed (derepressed) |
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Term
| What happens if tryptophan is present? |
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Definition
| The tryptophan acts as a co-repressor and binds to the trp repressor and they both bind to the operator, inhibiting RNA Polymerase |
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Term
| What does the trpL gene do? |
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Definition
| Encodes a leader peptide, with two tryptophan residues; this peptide can form hairpin loop structures |
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Term
| What happens when tryptophan levels are low? |
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Definition
Translation of trpL mRNA pauses, a hairpin loop structure forms
- inhibits formation of a terminator hairpin loop, and the trp operon is transcribed |
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Term
| When tryptophan levels are high? |
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Definition
The entire trpL mRNA is translated
- terminator hairpin loop can form, which terminates transcription of the trp operon |
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