Final answer:
Self-splicing refers to the ability of certain introns to remove themselves from the pre-mRNA molecule. Group I and Group II introns are examples of self-splicing introns.
Step-by-step explanation:
Self-splicing refers to the ability of certain introns to remove themselves from the pre-mRNA molecule. This process is catalyzed by the intron itself, without the need for external proteins or snRNPs. There are two types of self-splicing introns: Group I and Group II.
Group I introns are found in bacteria, mitochondria, chloroplasts, and some lower eukaryotes. They form a secondary stem-loop structure that positions catalytic nucleotides at splice sites, allowing them to excise themselves and re-ligate the exons.
Group II introns are found in chloroplasts, mitochondria, some bacterial mRNAs, and certain lower eukaryotes. They are longer and more complex, forming tertiary structures, but still have the ability to self-splice in vitro.