(a) Describe this process of synthesis of fully functional mRNA in a eukaryotic cell.
(b) How in the process of mRNA synthesis different from that in prokaryotes?

Explanation

(a) There are at least three RNA polymerases in the nucleus. There is a clear cut division of labour the RNA polymerase I trascribes rRNAs (288, 188, and 5.88). Where as the RNA polymerase III is responsible for transcription of tRNA, 5 SrRNA and SnRNAs (Small nuclear RNAs).
The RNA polymerase II transcribes precursor of mRNA, the heterogeneous nuclear RNA (hn RNA).
In prokaryotes, mRN A does not require any processing, so both transcription and translation occur in the cystol. It can be said that transcription and translation are coupled together.