Pre-mRNA splicing in yeast

The removal of introns from the primary transcript occurs by RNA splicing. Three major types of RNAs: tRNA, rRNA and mRNA, are known to contain introns. There are two general questions concerning any splicing mechanism: first, how is the precise recognition and alignment of the splice junctions achieved in introns whose lengths vary from a few hundred nucleotides to several thousands of nucleotides and, second, what are the biochemical mechanisms of the cleavage and ligation reactions.