Answer:
The given blank can be filled with operator.
Step-by-step explanation:
The proteins that assist in turning on or turning off the function of a specific gene by getting combined with certain sections of the DNA are known as transcription factors. The transcription factors that activate the transcription of a specific gene are known as activators, while that prevents transcription and is termed as repressors.
A repressor can be an RNA or a DNA binding protein, which prevents the articulation of genes by getting combined with the operator. A repressor, which binds with DNA prevents RNA polymerase from getting combined with the promoter, which further inhibits the transcription of the genes into mRNA.