In AP Biology Unit 6.3, transcription is the process where RNA polymerase reads a DNA template strand to synthesize a complementary RNA molecule. In prokaryotes, transcription occurs directly in the cytoplasm and the mRNA can be translated immediately with little or no modification. In eukaryotes, transcription happens inside the nucleus and the initial RNA transcript must undergo RNA processing, including the addition of a 5′ cap, a poly-A tail, and splicing to remove introns. These modificatio