There have been occasionally questions/comments about gene control. This should feed the hunger for knowledge. Here is an open access review article: Three-Dimensional Genome Organization and Function in Drosophila. It discusses some not widely known aspects of control of gene expression in Drosophila and at least some other metazoans (multi-cellular animals), including mammals. The main idea is the 3D structure of the DNA /chromosomes is involved in control gene expression, and proteins binding specific sequences are important to that. Loops of DNA are involved in how this works, and there are some diagrams illustrating the ideas. The complex functioning of the nucleus's information machine is amazing! The work to figure it out is impressive!