What is the functions of group I of introns?

Group I introns form a secondary structure with nine duplex regions. The cores of regions P3, P4, P6, and P7 have catalytic activity. Group I Introns Undertake Self-Splicing by Transesterification By changing the substrate binding site of a group I intron, it is possible to introduce alternative sequences that interact with the reactive G. Mobile introns are able to insert themselves into new sites. Mobile group I introns encode an endonuclease that makes a double-strand break at a target site. The intron transposes into the site of the double-strand break by a DNA-mediated replicative mechanism.