Problem:
I know that when RNA is transcribed from the original strand of DNA it contains introns and exons, and that the introns are spliced out of the strand to provide genetic diversity.
However, what I don't understand is, how does whatever is doing this splicing know whether the section it is reading is an intron or an exon?
Question: Are there start and stop codes like there are for polypeptides, or is it determined by epigenetic factors like methyl markers? Or is it neither?