Purpose: In order to investigate interspecies difference of intron size and the molecular mechanisms that alter it, we conducted extensive interspecies comparisons of homologous mammalian introns including the largest comparison between human and rodents.
Methods: Coding and non-coding DNA sequences of a gene were extracted from GenBank and orthologous relations of introns from two different species were identified by the assistance of the HOVERGEN software.
Results: The size of intron is significantly different among three mammalian orders (primates, artiodactyls, rodents), and a strong resemblance between the distribution of the size difference and the known distribution of insertion/deletion size is observed. Furthermore the size difference is larger for a intron in a genomic locus under a high mutation rate.
Conclusions: One of the major mechanisms that alter intron size is the biased frequency of short insertions and deletions, whose occurance is correlated to the point mutation rate of the genomic locus and whose accumulation depends on the life cycle of a organism.

XIIth International Biophysics Congress, 11-16 August 1996, Amsterdam, the Netherlands
(Poster presentation 13 Aug.)