Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Department

Biology

First Advisor's Name

Rene J. Herrera

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

George T. Duncan

Third Advisor's Name

DeEtta K. Mills

Fourth Advisor's Name

Bruce R. McCord

Fifth Advisor's Name

Timothy M. Collins

Keywords

Himalayas, Nepal, Tibet, Y-chromosome, mtDNA, Y-STR, Autosomal STR

Date of Defense

3-19-2012

Abstract

The Himalayan Mountain range encompasses an unparalleled landscape featuring some of the planet’s highest peaks, including Mount Everest. In the heart of this massive orographic barrier lies Nepal, sandwiched in the historically geostrategic position between the Tibetan plateau to the north and India in the south. Until recently, Nepalese and Tibetan populations remained poorly characterized genetically, partly because of their inaccessible geographical locations. In the present study, the genetic diversity of these two Himalayan populations is evaluated using different marker systems, including mitochondrial DNA (mtDNA) and Short Tandem Repeats (STRs) in the autosomes as well as on the Y-chromosome (Y-STR). While autosomal STRs are distributed throughout the genome and are biparentally inherited, the Y-chromosome and mtDNA are haploid markers and provide the paternal and maternal histories of the population, respectively. Fifteen autosomal STR loci were typed in 341 unrelated individuals from three Nepalese populations (188), namely Tamang (45), Newar (66) and Kathmandu (77), and a general collection from Tibet (153). These samples were also sequenced for the mtDNA control region and all of them were subsequently assigned to 75 different mtDNA haplogroups and sub-haplogroups by screening their diagnostic sites in the coding region using Restriction Fragment Length Polymorphism analysis and/or sequencing, thus achieving an unprecedented level of resolution. The results from the autosomal and mtDNA data suggest a Northeast Asian origin for the Himalayan populations, with significant genetic influence from the Indian subcontinent in Kathmandu and Newar, corroborating our previous Y-chromosome study. In contrast, Tibet displays a limited Indian component, suggesting that the Himalayan massif acted as a natural barrier for gene flow from the south. The presence of ancient Indian mtDNA lineages in Nepal implies that the region may have been inhabited by the earliest settlers who initially populated South Asia. In addition, seventeen Y-STR loci were analyzed in 350 Tibetan males from three culturally defined regions of historical Tibet: Amdo (88), Kham (109) and U-Tsang (153). The results demonstrate that the 17 Y-STR loci studied are highly polymorphic in all the three Tibetan populations examined and hence are useful for forensic cases, paternity testing and population genetic studies.

Identifier

FI12042312

Comments

The chapters 2, 3 and 4 are already published and the citations are provided in the copyright page.

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