An insertion polymorphism of LY1 retroposon in east Asians and its implications for the population studies of Koreans

We have examined a polymorphic LY1 retroposon insertion in the centromeric alphoid array of the Y-chromosome in samples from a total of 662 unrelated males from several ethnic groups of east Asia. The LY1 insertion polymorphism. was detected by PCR amplification using flanking primers of the Ll-alphoid junction, and electrophoresis on denaturing polyacrylamide gels followed by silver staining. Although the LY1 insertion frequencies varied among Chinese samples (mean: 6.0%), it was present at high frequencies in samples of the Miao (25.0%) and Han Chinese (21.4%), followed by Koreans (10.1%), Mongolians (8.8%), and Japanese (1.6%). This pattern of observed variation is similar to other recent surveys where it was found to be at the highest frequency in China, and was present at low frequencies in the surrounding areas, but most Caucasian and Negroid males examined so far completely lack the LY1 retroposon insertion. These findings would lead us to consider two possible explanations that Koreans are more likely related to the Chinese than to other east Asians, or that it is evidence of drift within the Korean population. The distribution pattern of LY1 insertion frequencies also reflected a common genetic affinity in contemporary populations from Korea and other parts of east Asia.