Reading Horiuchi et al: Alternative trans-splicing: a novel mode of pre-mRNA processing Biology of the Cell, Volume 98, Issue 2, 2006 http://www.ncbi.nlm.nih.gov/pubmed/16417469 Horiuchi's paper summarizes a number of findings concerning the subject of trans -splicing. Trans -splicing is a mechanism that naturally occurs in cells. It has also been experimentally used to correct genetic defects in mice, so it is both an interesting natural phenomenon and a possible avenue of investigation for therapeutic applications. Splicing, inside a cell, is one of the numerous steps from DNA to RNA to protein. Splicing operates on premature mRNA (pre-mRNA for short), from which it excises introns and joins the remaining exons back together. Splicing comes in two varieties: cis and trans . Cis -splicing joins exons within a single pre-mRNA molecule, while trans -splicing joins exons from different pre-mRNA molecules. Trans -splicing seems to be rare compared to cis -splicing, but it ...