Comparison between phylogeny of introns and exons in primates

Introns and exons of 7 genes ( epsilon globin, gamma-1 globin, gamma-2 glob in, delta globin, beta globin, Immunoglobulin and prepro-insulin) in primat es have been separated out and used to infer phylogeny respectively. For ea ch gene, results based on these two parts have been compared and showed tha t: ( 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) divergen ce time of orangutan deduced from different genes based on exons is various , while that based on introns is much similar, and consistent with fossil r ecords; (iv) there is a relationship between the G + C content and the subs titution rate. When the substitution rate of introns is higher than exons i n a gene, the G + C content of introns is less. The above results suggest t hat introns could provide useful evolutionary information among closely rel ated species.