Mitochondrial RNAs in trypanosomes are post-transcriptionally altered
by uridine insertion and deletion. The information for these RNA editi
ng processes, which are essential for the production of functional mes
sengers, is provided by small guide RNAs. This article discusses how f
eatures of partially edited RNAs, gRNAs and chimeric RNAs, in which a
gRNA is covalently linked to an editing site of pre-mRNA, have been us
ed for the construction of models.