Comparative Evolutionary Rates of
Introns and Exons in Murine Rodents
Austin L. Hughes, Meredith Yeager
Journal of Molecular Evolution
45:125-130 (1997)
Abstract
Analysis of DNA sequences of 132 introns and 140
exons from 42 pairs of orthologous genes of mouse and
rat was used to compare patterns of evolutionary
change between introns and exons. The mean of the
absolute difference in length (measured in base
pairs) between the two species was nearly five times
as high in the case of introns as in the case of
exons. The average rate of nucleotide substitution in
introns was very similar to the rate of synonymous
substitution in exons, and both were about three
times the rate of substitution at nonsynonymous sites
in exons. G+C content of introns and exons of the
same gene were correlated; but mean G+C content at
the third positions of exons was significantly higher
than that of introns or positions 1-2 of exons from
the same gene. G+C content was conserved over
evolutionary time, as indicated by strong
correlations between mouse and rat; but the change in
G+C content was greatest at position 3 of exons,
intermediate in introns, and lowest at positions 1-2
in introns.
