The correct answer is d: transcription can be turned off when a repressor binds to the DNA near the promoter. <span>The repressor is a protein which prevents a gene from being expressed (inhibits transcription from occurring). Near the promoter, there is a site called the operator, which is the binding site for the repressor. When the repressor binds, RNA polymerase is prevented from <span>binding to the promoter and initiating transcription. Gene expression is then turned off.</span></span>
14. compound 15. the concentration cannot be increased. 16. heterogenous mixtures 17. chocolate chip cookies 18. vegetable soup 19. a mixture is a pure substance a compound is not 20. Tastes sour
