Splicing of Messenger RNA Precursors

A decade has passed since the first description of RNA splicing and introns. In the interim, introns have been characterized in all lineages of eukaryotic organ-isms. The macromolecular structures of small nuclear ribonucleoprotein particles (snRNPs) and self-splicing RNAs have been discovered. The biochemical mech-anisms responsible for splicing of tRNAs, nuclear mRNA precursors, and self-splicing RNAs have been partially analyzed. These results have focused renewed attention on the role of RNA in biological systems and the evolutionary origin of genes. Intron Sequences Introns within nuclear genes encoding polypeptides have consensus sequences at their 5 ' and 3 ' splice sites (sequences shown in Fig. 1, where n ranges from 10 t