Which of the following mechanisms is (are) used to coordinate the expression of multiple, related genes in eukaryotic cells? A) Genes are organized into clusters, with local chromatin structures influencing the expression of all the genes at once. B) The genes share a common intragenic sequence, and allow several activators to turn on their transcription, regardless of location. C) The genes are organized into large operons, allowing them to be transcribed as a single unit. D) A single repressor is able to turn off several related genes. E) Environmental signals enter the cell and bind directly to promoters.