Editing occurs in a 3' to 5' direction within an 'editing domain':
In the example shown below, the A6 gene from Leishmania tarentolae,
the polarity of editing within the single editing domain is
determined by the creation of upstream anchor sequences for adjacent gRNAs by downstream editing. The initial gRNA
in a domain forms an anchor duplex with unedited sequence, but all subsequent gRNAs form anchors only with edited sequences.