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Evidence for the Ancestral Origin of Group I Introns in the SSUrDNA of Naegleria spp.
Author(s) -
JONCKHEERE JOHAN F. DE
Publication year - 1994
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/j.1550-7408.1994.tb06042.x
Subject(s) - biology , intron , naegleria , genetics , phylogenetic tree , group i catalytic intron , ribosomal rna , sequence (biology) , ribosomal dna , nucleic acid sequence , evolutionary biology , gene , rna , ribozyme , protozoa
The sequence variation within the group I intron in five Naegleria spp. was studied and compared with the sequence variation within the flanking small subunit ribosomal DNA. Considerable sequence divergence was observed in the introns as well as in the rDNA. In the intron deletions and insertions are only detected in the sequence contributing to the secondary structure, not in the open reading frame. Most of the sequence variation is detected in the unpaired loops. In the case of nucleotide substitution in helices, compensating base pair changes were observed. The sequence variation does not induce variation in the secondary structure model. The phylogenetic tree based on the intron sequences is similar to the tree based on the flanking rDNA sequences. This observation indicates that the intron might have been acquired at an early stage in evolution, and lost in the majority of Naegleria spp.