Answer:
If the petri plates are kept open for the longer duration of time then there are chances of cross contamination.
The contamination can be defined as growth of undesired microbes in the petri dishes or tubes which is no longer useful for the experiment.
The tube if kept open will develop the growth of contaminants in it. It can be cross contamination as well.
To avoid contamination the tubes and dishes should not be kept open for a longer duration of time.
Answer:
<h2>Catabolite repression
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Explanation:
1. Catabolite repression: it is the positive control of the lac operon.
2. It results in an increase in the rate of transcription. Here, the CAP protein is activated by cAMP which then bind to the lac operon and facilitate the binding of RNA polymerase to the promoter to transcribe the genes for lactose utilization.
3. Role of glucose in catabolite repression is that It stimulates transcription from the lac operon, causing an increase in cAMP levels in the cell. Glucose decreases the levels of cAMP in the cell, result in repressing transcription from the lac operon.
