A complete description of RNA transcription in eucaryotic cells must take into account the following distinctive features: (1) the two major ribosomal RNA (rRNA) components are initially synthesized as a complex precursor molecule, termed the rRNA transcription unit (RTU), which is significantly larger than its combined rRNA products; (2) the genes coding for the RTU are located in the nucleoli, and appear to be structurally remote from the genes specifying the 5 S rRNA and transfer RNA (tRNA) components; (3) a major part of the transcriptional activity in the nucleus results in the formation of large heterogeneous RNA molecules (N-RNA), some of which are precursors of cytoplasmic messenger RNA (mRNA) and others which do not leave the nucleus; (4) synthesis of the RTU is inhibited by doses of actinomycin 50–100 times lower than those needed to suppress synthesis of the other RNA species.
No takes yet. Share an insight, caveat, or question.
Perry et al. (1970) studied this question.