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| encode proteins that are used in metabolism or biosynthesis or that play a structural role in the cell |
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| genes whose products, either RNA or proteins, interact with other DNA sequences and affect the transcription or translation of those sequences |
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| A gene that is not regulated and is expressed continually |
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| affect the expression of sequences to which they are physically linked |
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Definition
| Gene regulation in which the binding of a regulatory protein to DNA stimulates transcription (the regulatory protein is an activator) |
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| negative control - more important in bacteria |
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Definition
| Gene regulation in which the binding of a regulatory protein to DNA inhibits transcription (the regulatory protein is a repressor) |
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| Set of structural genes in a bacterial cell along with a common promoter and other sequences (such as an operator) that control the transcription of the structural genes. |
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| DNA sequence in the operon of a bacterial cell. A regulator protein binds to the operator and affects the rate of transcription of structural genes |
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| Substance that stimulates transcription in an inducible system of gene regulation; usually a small molecule that binds to a repressor protein and alters that repressor so that it can no longer bind to DNA and inhibit transcription |
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Definition
| Operon or other system of gene regulation in which transcription is normally off. Something must take place for transcription to be induced, or turned on |
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Definition
| Stimulation of the synthesis of an enzyme by an environmental factor, often the presence of a particular substrate |
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Definition
| Operon or other system of gene regulation in which transcription is normally on. Something must take place for transcription to be repressed, or turned off |
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| Regulatory protein that binds to a DNA sequence and inhibits transcription |
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Term
| Negative inducible operon |
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Definition
| one in which an inducer prevents the repression of transcription |
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Term
| Positive inducible operon |
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Definition
| one in which an inducer activates an activator molecule to enable transcription |
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Term
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Definition
| encodes the lac Z, lac Y and lac A genes. Producing the beta-galactosidase, permease, and transacetylase proteins, respectively. Beta-galactosidase breaks down lactose into glucose and galactose. Permease helps lactose enter the cell |
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Term
Lac Operon
- Absence of Lactose |
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Definition
| The lac I gene is constitutive (always active) and constantly makes the repressor molecule. The repressor binds to the operator and prevents transcription of the genes. This is not completely successful and a low level (basal level) of transcription does occur. |
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Term
Lac Operon
- Presence of Lactose |
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Definition
| Lactose binds to the repressor molecule and prevents the repressor from binding to the operator. Without the repressor transcription can ensue. The cell therefore has the proteins needed for lactose metabolism |
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Term
Lac Operon
- Glucose is Low |
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Definition
| If glucose is low then cAMP is high. This is regulated by a different mechanism. cAMP will bind to a constitutive protein called catabolite activator protein (CAP). This complex binds to the lac promoter causing a bending of the DNA that stabilizes RNA polymerase on the promoter. |
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Term
Lac Operon
- Glucose is High |
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Definition
If glucose is high then cAMP is low. This is regulated by a different mechanism.
The CAP protein does not bind the cAMP molecules because there are so few molecules. The RNA polymerase is not stable on the promoter and can easily disengage. |
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Term
| catabolite activator protein (CAP) |
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Definition
binds to the promoter of the lac operon and stimulates transcription. CAP must complex with adenosine-3′, 5′-cyclic monophosphate (cAMP) before binding to the promoter of the lac operon. The binding of cAMP–CAP to the promoter activates transcription by facilitating the binding of RNA polymerase. Levels of cAMP are inversely related to glucose: low glucose stimulates high cAMP; high glucose stimulates low cAMP.
The binding of the cAMP–CAP complex to DNA produces a sharp bend in DNA that activates transcription. |
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