Methods DNAs were extracted from the white blood cells of people in Hainan by salt-out method. Polymerase chain reaction and restriction endonuclease was used to determine the 4533G/A polymorphism.

• 方法用盐提取法提取人群中白细胞的DNA,以聚合酶链反应、限制性内切核酸酶检测-4533G/A多态性。