question: Does splicing occur co-transcriptionally?
answer: The consensus view, based on four organisms, is that the majority of splicing events take place co-transcriptionally in most cells and tissues. RNA processing events that take place on the transcribed pre-mRNA include capping, splicing, editing, 3' processing, and polyadenylation. Most of these processes occur co-transcriptionally while the RNA polymerase II (Pol II) enzyme is engaged in transcriptional elongation.