Before revision:  During the active period of the gene, many RNAP molecules transcribe the gene to synthesize the mRNA . The binding event of RNAP to the active state of the gene is an probabilistic process and therefore, introduces noise or fluctuations in the protein levels. The binding event of RNAP to the active state of the gene is an probabilistic process and therefore introduces noise in the protein levels.
After revision:  During the active period of the gene, many RNAP molecules transcribe the gene to synthesize the mRNA . The binding event of RNAP to the active state of the gene is an probabilistic process and therefore, introduces noise or fluctuations in the mRNA and protein levels.