Y-chromosome and mtDNA studies into the population structure of the Christmas Island community

Abstract

Christmas Island is a remote Australian territory located close to the main Indonesian island of Java, and 1,540 km from the coast of Western Australia. The Island was annexed by Great Britain in 1888 and indentured Chinese labourers were recruited to mine the phosphate deposits. After WWII additional labourers were hired from Malaysia. The present population comprises approximately 60% Chinese, 25% Malay and 15% European or other. To determine the genetic structure of the Christmas Island population, markers on the Y-chromosome and mitochondrial DNA (mtDNA) were investigated in 92 individuals. Y-chromosome biallelic polymorphisms revealed moderate to high frequencies of markers M95 (15%), M119 (23.3%) and M122 (36.7%), consistent with ancient male origins in Southern China and SE Asia. mtDNA hypervariable segment I (HVS-I) sequences revealed high levels of genetic similarity to the Southern Chinese, Hong Kong Cantonese, Indonesian Moluccas and Thai. The mtDNA COII/tRNALys 9-bp deletion was present at a relatively high frequency (31.5%), and in conjunction with the HVS-I polymorphisms suggested two distinct origins from China and SE Asia. The present study provides a useful model for the investigation of contemporary populations derived from different origins and could play an important role in the study of inherited disease