23.1 Introduction 23.2 Group I introns undertake self-splicing by transesterification 23. 3 Group I introns form a characteristic secondary structure 23. 4 Ribozymes have various catalytic activities 23.5 Some introns code for proteins that sponsor mobility 23. 6 The catalytic activity of RNAase P is due to rna 23. 7 Viroids have catalytic activity 23. 8 RNA editing occurs at individual bases 23 9 RNA editing can be directed by guide rnas 消当23.1 Introduction 23.2 Group I introns undertake self-splicing by transesterification 23.3 Group I introns form a characteristic secondary structure 23.4 Ribozymes have various catalytic activities 23.5 Some introns code for proteins that sponsor mobility 23.6 The catalytic activity of RNAase P is due to RNA 23.7 Viroids have catalytic activity 23.8 RNA editing occurs at individual bases 23.9 RNA editing can be directed by guide RNAs