Answer:
Silencer
Step-by-step explanation:
Gene expression is regulated by many upstream and downstream regulatory sequences. A regulatory site may serve as a binding site for positive or negative transcription factors to regulate gene expression. A regulatory site that binds negative regulators/ transcription factors to control transcription is called a silencer.
In the given example, the deletion of a DNA sequence outside the protein-coding region of the beta-globin gene resulted in an increased rate of expression. This means that the deleted sequence was a silencer and served to inhibit the expression of the beta-globin gene.