Comparison between phylogeny of introns and exons in primates

Introns and exons of 7 genes ( epsilon globin, gamma-1 globin, gamma-2 globin, delta globin, beta globin, Immunoglobulin and prepro-insulin) in primates have been separated out and used to infer phylogeny respectively. For each gene, results based on these two parts have been compared and showed that: ( i ) the topology of introns is almost consistent with that of exons in each gene, while the branch length of them varies, because of the different mutation rate; ( ii ) there is evidence that the substitution rate of exons would decrease in hominoids, but that of introns would not; (iii) divergence time of orangutan deduced from different genes based on exons is various, while that based on introns is much similar, and consistent with fossil records; (iv) there is a relationship between the G + C content and the substitution rate. When the substitution rate of introns is higher than exons in a gene, the G + C content of introns is less. The above results suggest that introns could provide useful evolutionary information among closely related species.