Like the lac operon, the trp operon is a negative control mechanism. The lac operon responds to an inducer that causes the repressor to dissociate from the operator, derepressing the operon. The trp operon responds to a repressor protein that binds to two molecules of tryptophan.
The distribution of natural resources depends upon number of physical factors like terrain, climate and altitude. The distribution of resources is unequal because these factors differ so much over the earth.
