10.1 Introduction Regulatory region prom oter Startpoint Structural genes Prom oter GENE OFF BY DEF AULT AAAAAAAAAAAAAAA RNA Factors int erad wth rNa pol ym erase GENE TURNED ON BY ACTIVATORS 八AA RNA www' Single protein Figure 10. 3 In positive control, trans-acting factors must bind to cis-acting sites in order for RNa polymerase to initiate transcription at the promoter In a eukaryotic system, a structural gene is controlled individually 请莘大Figure 10.3 In positive control, trans-acting factors must bind to cis-acting sites in order for RNA polymerase to initiate transcription at the promoter. In a eukaryotic system, a structural gene is controlled individually. 10.1 Introduction