RESUMEN
<p><b>OBJECTIVE</b>To study the frequency of a 9 bp deletion polymorphism of mitochondrial DNA (mtDNA) in ethnic Miao, Buyi and Dong populations from Guizhou province.</p><p><b>METHODS</b>Polymerase chain reaction-polyacrylamide gel electrophoresis (PCR-PAGE) was used to detect the 9 bp deletion. The result was verified with DNA sequencing.</p><p><b>RESULTS</b>Two polymorphisms, including a standard pattern and a short pattern (the 9 bp deletion), were found among the three ethnic groups. The frequency of short pattern in 304 males was 23.0%. Respectively, those of Miao, Buyi and Dong ethnics were 28.6%, 26.8% and 13.7%. A statistically significant difference was detected among the three groups (P<0.05).</p><p><b>CONCLUSION</b>The frequencies of the 9 bp polymorphism were relatively high among ethnic Miao, Buyi and Dong populations from Guizhou, and there was a significant difference between the three.</p>