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.
After revision:  During the active period of the gene, many RNAP molecules transcribe the gene to synthesize the mRNAs . 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.