10.1 Introduction T he cis acting cp er ato r/prom ce r sites are a da ce nt tot he str ud ural genes Figure 10.2 In Regul atory region Strucural gene(s negative control, 八 M a trans-acting Genes are on because RN Polymerase initiates transcr ption at prom oter repressor binds to the cis-acting operator to turn off transcription RNA n prokaryotes, ySeveralp rc eins p° multiple genes are controlled Genes are tumed off when repressor binds to ope rator coordinate Repressor 消当Figure 10.2 In negative control, a trans-acting repressor binds to the cis-acting operator to turn off transcription. In prokaryotes, multiple genes are controlled coordinately. 10.1 Introduction