Final answer:
Expressed protein-coding genes make up the majority of most bacterial genomes and are regulated at the transcriptional level.
Step-by-step explanation:
The majority of bacterial genomes are made up of expressed protein-coding genes. These genes encode products that serve as cellular structures or enzymes. In prokaryotes, such as bacteria, gene expression is primarily regulated at the transcriptional level. This ensures that only the necessary proteins are produced at a given time, preventing the waste of cellular resources.