Question

what does the sentence "the sequences that comprise the genes constitute most of a bacterial genome "

Answer 1

"The sequences that comprise the genes constitute most of a bacterial genome” means that bacterial genome contains mostly coding region unlike eukaryotes whose 98% of the genome is non-coding regions.

Bacteria have very small genome compared to eukaryotes. They can’t afford to have non-coding regions. In fact, bacteria have poly-cistronic genes whereby a single open-reading frame constitutes many protein genes.

Coding regions encode proteins (via mRNA), while non-coding regions encode tRNAs, rRNAs, other small RNAs, repetitive DNA sequences, junk DNA elements, etc.