Transcription and RNA processing
A promoter helps position transcription machinery. For a particular gene, one DNA strand serves as template; its RNA is complementary and antiparallel. The coding strand matches the RNA sequence except that DNA has T where RNA has U. In eukaryotes, a 5′ cap, poly-A tail, and splicing help produce functional mRNA. Alternative splicing can yield different products from the same gene. Bacterial transcription and translation can overlap because there is no nuclear envelope separating them.
Template DNA 3′-TAC GGA-5′ produces RNA 5′-AUG CCU-3′. Removing different combinations of exons from a pre-mRNA can produce distinct mature transcripts.
RNA is not a copy of both strands glued together. Also, splicing changes the RNA product, not the genomic sequence.