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Group II introns are a novel class of RNAs best known for their self-splicing reaction. Under certain in vitro conditions, the introns can excise themselves from precursor mRNAs and ligate together their flanking exons, without the aid of protein. The splicing mechanism is essentially identical to splicing of nuclear pre-mRNA introns, and this similarity has led to the widespread belief that group II introns were the ancestors of spliceosomal introns, which make up 25% of the human genome.
Some group II introns have a second remarkable property: they encode reverse transcriptase (RT) ORFs and are active mobile elements. Such mobile group II introns can insert into defined sites at high efficiencies (called retrohoming), or can invade unrelated sites at low frequencies (retrotransposition).
| Introduction | Intron secondary structure | Intron ORF structure | Introns listed by organism | Bacterial intron fragments | Alignment of insertion sequence |
| Phylogenetic tree of intron ORFs | How to find group II intron | Site map | Contact us |