Classify the given examples of prokaryotic gene expression as positive or negative gene regulation.
Positive gene regulation Negative gene regulation



1. In the presence of iron, the dux repressor protein binds DNA. and the gene that encodes for the diphtheria toxin is not expressed
2. In the presence of excess tryptophan, a repressor protein binds the operator of the trp operon and prevents the operon from being transcribed.
3. In the presence of the sugar rabinose, an activator protein binds the promoter of the genes responsible for processing arabinose and induces their transcription
4. In the absence of lactose, the lack repressor protein binds the loc operon