Positive control
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The term positive control has several meanings.
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[edit] Testing Usage
A positive control is a reactant that causes a known effect when applied to a cluster of test organisms. Benedict's reagent is an example of this. The positive control in experiments reveals that a certain procedure works according to expectations and actually gives you the expected results. It demonstrates that the experiment is functioning as it should; in general practice this means that your subject(s) are exposed to a substance that is known to have a certain effect. Contrast this with the negative control, (or standard scientific control) where you expose your subject (or experiment) to a substance or condition that is known to have no effect.
[edit] Phrase
One says that positive control has been achieved when what happens is what was intended to happen and that's all that happens. The Columbia accident demonstrated that NASA had not achieved positive control of the Shuttle Program.
[edit] Aviation Usage
In air traffic control, positive control is the practice of controlling aircraft whose positions are determined by direct radar observation.
[edit] Genetics Usage
Positive control is a type of gene expression where the transcription is switched on when a regulatory protein binds to the DNA. The regulative protein is namned transcriptional activator or gene activator protein.
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