RESUMO
Branch-Site Model is a statistical method for detecting molecular adaptation at individual along specific lineages. Not only the model could indicate whether genes in phylogeny under the positive selection or not, but also could forecast positive selection sites in these genes. The sites promote divergence and polymorphism of genes. Chemokines are chemotactic cytokines that can induce immune cells migration, conducting their functions via chemokine receptors. In the test, the molecular adaptation of chemokines and chemokines receptors genes had been analyzed by Branch-Site model. The results showed that only a few of genes, such as RANTES and CCR5, are in the course of positive selection. Several CCR5 positive selection sites are located in a region that involved in binding to receptor and its chemokine.
