Evolution of group II introns

Table 2 Distribution of intron classes in different organisms and organelles

	Eubacteria	Archaebacteria	Mitochondria	Chloroplasts
RNA-based classes^a
IIA	X		X	X
IIB	X	X	X	X
IIC	X
IEP-based classes^b
CL	X	X	X	X
ML	X		X	X
A	X
B	X
C	X
D	X	X
E	X	X
F	X

^aClasses of introns based on the ribozyme structural characteristics. ^bClasses of introns based on phylogenetic groupings of the IEPs. CL, chloroplast-like; IEP, intron-encoded protein; ML, mitochondrial-like.

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