Understanding the central dogma of biology, DNA (genes) begets mRNA begets proteins will help to understand this questions. Currently it is thought, although there has been recent discoveries of nucleic acid miRNA, that the protein product of a gene will regulated the production of other proteins and itself. This sort of regulation primarily acts as a negative feedback loop. For example if more of gene A that gets made into protein, then either the protein itself or other messengers will slow down that gene A's output.