What is the Difference Between Group I and Group II Introns?

Group I and Group II introns are both self-splicing introns, meaning they can excise themselves from RNA transcripts and ligate their flanking RNA sequences without the help of any proteins. However, they differ in several aspects:

1. Distribution: Group I introns are found in bacteria, bacteriophages, and eukaryotes (organellar and nuclear genomes), while Group II introns are present in bacteria, archaea, and eukaryotic organelles.
2. Splicing Mechanism: The splicing reaction in Group I introns is initiated by a guanosine cofactor, while in Group II introns, the splicing reaction is initiated by internal adenosine.
3. Lariat Structure: Group II introns form a lariat-like structure during the splicing process, while Group I introns do not.
4. Subgroups: Group II introns have three major subgroups (IIA, IIB, and IIC) and further subdivisions, which differ in their peripheral structures and active sites. Group I introns, on the other hand, have different subgroups that mainly differ in peripheral structures.

Both Group I and Group II introns are mobile genetic elements and are used as tools in biotechnology and molecular medicine.

Comparative Table: Group I vs Group II Introns

Group I and Group II introns are self-splicing introns that are found in different organisms and play crucial roles in genome dynamics. Here is a table highlighting the differences between Group I and Group II introns:

In summary, Group I and Group II introns are large ribozymes that catalyze a transesterification reaction to splice themselves out of RNA transcripts. They are found in all three domains of life and are used as tools in biotechnology and molecular medicine. However, they differ in their initiation of the splicing reaction, their location, and the structure they form during the splicing process.