Which of the following statements about gene regulation concerning operons is incorrect? a) a negative repressible gene is controlled by a regulatory protein that inhibits transcription. b) for a gene under negative repressible control, a small molecule is required to prevent the gene's repressor from binding to dna. c) for a gene under positive repressible control, the normal state is transcription of a gene, stimulated by a transcriptional activator. d) a regulator gene has its own promoter and is transcribed into an independent mrna. e) presence of operons where genes of related functions are clustered is common in bacteria but not in eukaryotes.