Final answer:
Gene expression is regulated by transcription and translation, products of other genes, and environmental exposure.
Step-by-step explanation:
Gene expression is regulated at many levels, including epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels.
Transcription and translation are processes that occur during gene expression and regulate the phenotypic expression of genes.
Products of other genes can also regulate gene expression by interacting with other genes through various pathways.
Environmental exposure, such as exposure to certain chemicals or temperature, can also influence gene expression.
Therefore, the correct option is All of the above.