Analysis Of Ancient Mitochondrial DNA From The Lajia Ruins In Minhe County Of Qinghai Province

Lajia ruin is in Minhe county of Qinghai province. The climate of Lajia ruin is fine because of its location in Guanting basin at upper Yellow River. The cause of Lajia ruin may be a sudden disaster deducing from the remains in the ruins, which is different from other history ruins. This study tries to conclude the maternal relationship among the individuals of the human remains, also the genetic relationship between the ancient population and compared populations.Ancient DNA was extracted from the teeth nearly 3800 years old. After successfully amplification and sequencing, 14 nucleotide sequences of 325bp length in hypervariable regionⅠof the mtDNA control region were gotten. Eight haplotypes with 13 polymorphic sites in 14 individuals were obtained. Samples Y2 and Y10 shared the same haplotype with the transitions in sites 16223(C→T) and 16362(T→C). Samples Y5 and Y6 shared the same haplotype with the transitions in sites 16223(C→T), 16256(C→T) and 16260 (C→T). Samples Y8 and Y11 shared the same haplotype with the transition in sites 16223(C→T) and 16311(T→C). Samples Y7,Y12,Y13 and Y14 shared the same haplotype with the transitions in sites 16223(C→T),16298(T→C) and 16327(C→T). Each of the four groups was considered to separately arise from same maternal lineages.Base on the specific mutation sites in mtDNA HVS Ⅰ and the haplogroups of sharing sequences, the sequences of Lajia specimens belonged to haplogroup B, M10, C, D and M* motifs. Haplogroup M10 exists mainly in north of China and seldom in south of China. Haplogroup B, C, D is the principal haplogroups in East Asia. While haplogroup M* is composed with those old haplotypes in Asia which cannot be classified to the other haplogroups. Three of 14 ancient Lajia specimens were considered to belong to haplogroup M10 motif. This suggests that compared with the populations in south of China, Lajia ancient specimens have closer relationship with north ones.Phylogenetic analysis showed that Lajia ancient specimens occupied a position in branches of East Asia and were far away from the branches of Europe, Central Asia and North Asia. Moreover, Lajia ancient specimens presented shorter genetic distance to Tibetan population of Qinghai and Yunnan than to other modern populations. This suggests that Lajia ancient specimens probably have closer relationship with the ancestor of Tibetan in maternal lineage.The multidimensional analysis of Lajia ancient population and other related populations were carried on. The result showed that Lajia ancient population was near the Tibetan from Qinghai and Yunnan, Qinghai Mongolian and Xi'an Han. This suggests that the genetic character of Lajia ancient population is probably related with its geographic distribution. The mtDNA gene pool of that region is continual on some extent.Phylogenetic network of mtDNA was constructed with Lajia and 11 other ancient populations. The backbone type was defined as a center of a star having>10 descendant types. On the basis of the star like clusters, we identified six radiation groups. Then we calculated the frequency of each of 11 populations in every group and constructed PC map. The map shows that Lajia ancient population has closer relationship with Jiangjialiang and Dulan ancient populations.14 Lajia ancient specimens were mainly in group one and group two, accounting for 78% and 14%. The result is similar with the modern populations in East Asia and suggests further that Lajia ancient population has a closer genetic relationship with modern East Asian populations.