Final answer:
Gene Q, which stops and starts the expression of other genes, is a regulatory gene, playing a crucial role in gene expression regulation at various levels, including epigenetics, transcription, and translation.
Step-by-step explanation:
Gene Q is described as being responsible for the starting and stopping the expression of other genes. Therefore, Gene Q is a(n) regulatory gene. Regulatory genes are critical components in the cascade of gene expression, enabling cells to perform complex functions and respond to environmental changes. They are involved in various processes, including epigenetic modifications, transcriptional control, and gene expression regulation. For instance, regulatory genes can influence gene expression by altering histone acetylation, which can lead to gene silencing or activation. Moreover, the use of energy-providing molecules like guanine triphosphate (GTP) by protein factors such as eukaryotic initiation factor-2 (eIF-2), highlights the necessity of regulation even during the translational phase of gene expression. In the case of prokaryotic cells, regulatory genes often operate within an inducible operon structure which can modulate gene expression in response to environmental changes.