Sunday, August 24, 2008

More on Haplogroup X

Am J Hum Genet. 2001 July; 69(1): 237–241.
The Presence of Mitochondrial Haplogroup X in Altaians from South Siberia

"A striking example of the presence in American Indians of genotypes not from haplogroups A–D is haplogroup X. This haplogroup represents a minor founding lineage that is restricted in distribution to northern Amerindian groups, including the Ojibwa, the Nuu-Chah-Nulth, the Sioux, and the Yakima, as well as the Na Dene–speaking Navajo (Brown et al. 1998). Unlike haplogroups A–D, haplogroup X is also found at low frequencies of ~4% in western Eurasian populations. Despite a shared consensus RFLP haplotype, substantial genetic differences exist between the American Indian and European haplogroup X mtDNAs. Phylogenetic analysis and coalescence estimates for American Indian and European haplogroup X mtDNAs exclude the possibility that the occurrence of haplogroup X in American Indians is due to recent European admixture. They also clearly indicate that the two branches/subgroups are distantly related to each other and that considerable genetic substructure exists within both groups (Brown et al. 1998).

Haplogroup X is remarkable in that it has not been found in Asians, including Siberians, suggesting that it may have come to the Americas via a Eurasian migration. The virtual absence of haplogroup X in eastern and northern Asia raises the possibility that some American Indian founders were of European ancestry. In that case, as it has been proposed, haplogroup X was brought to America by the eastward migration of an ancestral white population, of which no trace has so far been found in the mtDNA gene pool of modern Siberian/eastern Asian populations (Brown et al. 1998)."

1. The Druze: A Population Genetic Refugium of the Near East. PLoS ONE. 2008 May 7;3(5)

2. Origin and Diffusion of mtDNA Haplogroup X, Am J Hum Genet. 2003 November; 73(5): 1178–1190.

3. The Presence of Mitochondrial Haplogroup X in Altaians from South Siberia
Am J Hum Genet. 2001 July; 69(1): 237–241.

4. Distribution of mtDNA haplogroup X among Native North Americans. Am J Phys Anthropol. 1999 Nov;110(3):271-84.

5. Rohde, DLT , On the common ancestors of all living humans. Submitted to American Journal of Physical Anthropology. (2005)

6. Rohde DLT, Olson S, Chang JT (2004) "Modelling the recent common ancestry of all living humans". Nature 431: 562-566.


cadams said...

Thank you for these three X files. Fascinating!

Native American Geneticist said...

Thanks for the update. I would agree, we don't really know where haplogroup X comes from. However, because population sizes are so small, we still do not know much and have lots to learn.

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