Preliminary Study On The Origin Of Tibetan Ethnic Population In Tibet

Preliminary Study on the Origin of Tibetan Ethnic Population in TibetObjectiveThe purpose of this paper was to obtain the polymorphism information of mitochondria DNA and Y chromosome DNA on Tibetan ethnic population in Tibet for exploring the origin of Tibetan ethnic population with maternal and paternal inheritance, to provide the reference data for individual identification of Tibetan ethnic population, and to evaluate the somatotype of the Tibetan adolescent for obtaining the character and developmental regularity of the Tibetan ethnic population, to compare the Tibetan somatotype with the other groups' in order to analyzing the origin of Tibetan ethnic population with somatotype, and to investigate the parameter of dermatoglyphics on Tibetan ethnic population for accumulating the dermatoglyphical data of Tibetan ethnic population and exploring the origin of Tibetan ethnic population with dermatoglyphicsMethodsThe 2592 samples who were healthy and lived in Tibet all the time were selected from unrelated adolescents aged from 7 to 20 years old in nine schools of Tibet with stratified cluster sampling method. 12 anthropometric measurement indexes including height, weight, hand length and so on were measured. The somatotype were evaluated by Heath-Carter somatotyping method. 11 dermatoglyphical parameters including the type of finger and palm, finger ridge count, atd angle and so on were assessed, mtDNA region Vand DYS287 locus were amplified and typed by gelose electrophoresis. The polymorphism of mtDNA Hypervariable regionⅠwas amplified by polymerase chain reaction, then sequenced on ABI-3100Avant. Compared to Combridge reference sequence, the sequences were sorted by ClustalW database in EBI software. The position and type of variation were found and arranged. Phylogenetic tree was constructed by MEGA2.1 software and the genetic structure of Tibetan ethnic population in Lhasa and Naqu was analysed by AMOVA program in Arlequin2.0. Results1. Compared to Combridge reference sequence, the sequence of Lhasa and Naqu were detected 31and 36 haplotypes, 51 loci, 141and 128 base conversion (89.81% and 88.89% total mutation), the positions of mutational hot spot were np16223 and np16362, the frequency of mutations in Lhasa and Naqu was 90.32%, 64.51% and 83.33%, 58.33% respectively. The nucleotide diversity in Lhasa and Naqu was 0.016058±0.008740, 0.016084±0.008795 respectively. The poly-C haplotype of Lhasa and Naqu in np16180-np16194 was 4 and 9 respectively. The mismatch distribution curve of Lhasa and Naqu were single peak, the Tau values was 6.331 and 5.590 respectively. The expending time of Lhasa Tibetan ethnic population was 53 thousands years ago and Naqu Tibetan ethnic population was 42 thousands years ago. The variation between Lhasa and Naqu population is 0.96 % (P=0.1212). Phylogenetic tree shows Lhasa and Naqu population first clustering, then Han nationality of Xi'an, Mongolian and other East-Asian group clustering, finally, the African and all population clustering. The genetic diversity of Lhasa and Naqu is 0.9862 and 0.9961, respectively. The genetic identity of Lhasa and Naqu is 0.0466 and 0.0316, respectively.2. We detected two gene types that was normal type and the type of 9bp deletion in mtDNA region V. The frequency of 9bp deletion was 4.88% in Lhasa group, 6.17% in Naqu group and the total frequency of 9bp deletion was 5.52%. There was no significant difference between Lhasa group and Naqu group in mtDNA region V 9bp deletion(X~2=0.131, P＞0.05).3. We observed two gene types: YAP~+ and YAP in DYS287 locus. The frequency of YAP~+ 54.28%, of the total was 4.46%, 62.50 in Lhasa and Naqu respectively. There was no significant difference between Lhasa group and Naqu group in DYS287 locus YAP~+(X~2=4.46, P＜0.05).4. The average somatotype of Tibetan adolescents in male is Mesomorphic Ectomorphy (2.40-3.29-3.72); in female, the average somatotype is central (3.65-2.87-3.32). The somatotype growth of Tibetan adolescents has special regularities: with age increasing the somatotypes develop from mesomorph-ectomorphy, mesomorphtic ctomorphy to mesomorph-ectomorphy in male, however, in female from Ectomorph-Endomorphy, Balanced Ectomorphy, Ectomorph-Endomorphy Ectomorphic Endomorphy to Balanced Endomorphy.5. In Tibetan ethnic population, whole(58.99%) was the dominant fingerprint type, Loop(38.25%) was secondly, arch(2.76. %) was the lowest. We observed the highest frequency on the combination pattern of five finger in one hand was 5W. Total finger ridge count was 144.75 in male, in female was 133.87 and the mean was 139.01. Total finger ridge count, ab finger ridge count, ad finger ridge count and td finger ridge count all showed man more than female, and significantly in total finger ridge count and td finger ridge count. Atd angle was 42.95°and 43.28°respectively in male and female. Atd angle showed right more than left in male, in female conversely. In palm crease, popular type (81.15%) was dominant, Sydney type (1.31%) was lowest and the frequency of simian line was 2.03%. The density of dermatoglyphics in Tibetan adolescents descent with age increasing, and differed in sex(P×0.05), man's more than female's.Conclusions1. Nucleotide diversity of Tibetan mtDNA is high, is closer to East Asian and Mongolian, and phylogenetic tree show the relation between Tibetan and East Asian and Mongolian is closer; the significant difference was not found between Lhasa and Naqu population. The study provides basic datas of Tibetan mtDNA D-loop for forensic medicine, these results suggest that sequence Polymorphism of mtDNA control region would be very useful in forensic practice as a marker for individual identification.2. The frequency of mtDNA regionⅤ9bp deletion in Tibetan ethnic population is similar to the races which origin from northen like Mongolia nationality, so it confirms that Tibetan ethnic population belongs to northern group in our country.3. Tibetan YAP~+ frequency of DYS287 locus is higher, and highest in Naqu(62.5%), so we conclude that the Tibetan ethnic population in Naqu is a isolate and they are the optimal samples to explore the origin of Tibetan ethnic population.4. The somatotypes of Tibetan adolescent in male are more slender and muscles are stronger, the shape is more slender and body fat is more in female. During the period of growing and developing quickly, the difference of the somatotypes of Tibetan adolescents between city(Lhasa) and pasture (Naqu) were significant and the nutritional status of city is prior to pasture. Compared with the other eight groups (like Han nationality and so on), body fat is less and skeleton and muscles are not very strong in Tibetan adolescents.5. The somatotype of Tibetan ethnic population is the most closed to Han nationality, and similar to nomads like Mongolian and dsfasfs, but differs from nordic (Finland, Hungary) and melanian (Nigeria). So we can conclude from somatotype that there are the common ancestor Tibetan ethnic population and Han nationality.6. The density of dermatoglyphics of Tibetan adolescents descent with age increasing, and differed in sex. Ab density of dermatoglyphics and ad density of dermatoglyphics show man more than female. The density of dermatoglyphics of Tibetan adolescents is more than Han nationality's. It is concluded that Tibetan ethnic population is closd to Han nationality and Diqiangshi nationality, however farther to Indian and Bengal through clustering 57 groups like Tibetan ethnic population.