Two complexities that are observed in the process of transcription in eukaryotes and not in Prokaryotes are as follows
i. There are three RNA polymerases in the nucleus RNA polymerase I transcribes - rRNAs, RNA polymerase II transcribes - heterogenous nuclear RNA/hnRNA, RNA polymerase III transcribes - tRNA/5 srRNA/snRNA (small nuclear RNAs).
ii. Primary transcripts/hnRNA contain both the exons and non functional introns, subjected to splicing where introns are removed, exons are joined in a defined order, hnRNA undergoes processing called capping and tailing, In capping nucleotide methyl guanosine triphosphate is added to 5' end of hnRNA, In tailing adenylate residues (200-300) are added at 3"- end in a template independent manner, this fully processed hnRNA is now called mRNA (and transported out of the nucleus for translation).