Complex sentence: However, the rescue mRNA has a modified 5'-UTR (untranslated region) so that the rescue mRNA contains no target for the Morpholino but the rescue mRNA's coding region encodes the protein of interest.
Split into simpler sentences: However, the rescue mRNA has a modified 5'-UTR (untranslated region) so that the rescue mRNA contains no target for the Morpholino. The rescue mRNA's coding region encodes the protein of interest.