If loss of a control element causes an increase in gene expression, what must be the normal role of that control element? propose a biological explanation for how the loss of such a control element could lead to an increase in gene expression.

The normal role of this control element can be that of a negative modulator or regulator

Explanation:

For example, the lactose operon in the bacteria Escherichia coli is negatively regulated. In lactose absence a represor protein is produced, which inserts in the DNA operator site blocking transcription of structural genes. if for example a mutation affects the synthesis of  this repressor, expression of structural genes will increase with no regulation.

A mutation in the DNA operator site that avoids insertion of the repressor, too.

A mutation in the gene that codes for the repressor, will also do the job

kelp are large brown algae that live in cool, relatively shallow waters close to the shore. they grow in dense groupings much like a forest on land. these underwater towers of kelp provide food and shelter for thousands of fish, invertebrates, and marine mammal species.

e) all of the above