Haplogroup X (mtDNA)

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Haplogroup X
Time of origin 30,000 YBP
Place of origin Asia
Ancestor N
Descendants X1, X2
Defining mutations 73, 7028, 11719, 12705, 14766, 16189, 16223, 16278[1]

In human mitochondrial genetics, Haplogroup X is a human mitochondrial DNA (mtDNA) haplogroup which can be used to define genetic populations.

Contents

[edit] Origin

The genetic sequences of haplogroup X diverged originally from haplogroup N, and subsequently further diverged about 20,000 to 30,000 years ago to give two sub-groups, X1 and X2.

[edit] Distribution

Overall haplogroup X accounts for about 2% of the population of Europe, the Near East and North Africa. Sub-group X1 is much less numerous, and restricted to North and East Africa, and also the Near East. Sub-group X2 appears to have undergone extensive population expansion and dispersal around or soon after the last glacial maximum, about 21,000 years ago. It is more strongly present in the Near East, the Caucasus, and Mediterranean Europe; and somewhat less strongly present in the rest of Europe. Particular concentrations appear in Georgia (8%), the Orkney Islands (in Scotland) (7%) and amongst the Israeli Druze community (26%); the latter are presumably due to a founder effect.

[edit] North and South America

Haplogroup X is also one of the five haplogroups found in the indigenous peoples of the Americas.[2] Although it occurs only at a frequency of about 3% for the total current indigenous population of the Americas, it is a major haplogroup in northern North America, where among the Algonquian peoples it comprises up to 25% of mtDNA types. It is also present in lesser percentages to the west and south of this area — among the Sioux (15%), the Nuu-Chah-Nulth (11%–13%), the Navajo (7%), and the Yakima (5%).

Unlike the four main Native American haplogroups (A, B, C, and D), X is not at all strongly associated with East Asia. The main occurrence of X in Asia discovered so far is in Altaia in South Siberia[3], and detailed examination[4] has shown that the Altaian sequences are all almost identical (haplogroup X2e), suggesting that they arrived in the area probably from the South Caucasus more recently than 5000 BP.

Two sequences of haplogroup X2 were sampled further east of Altai among the Evenks of Central Siberia[4]. These two sequences belong to X2* and X2b. It is uncertain if they represent a remnant of the migration of X2 through Siberia or a more recent input.

This relative absence of haplogroup X2 in Asia is one of the major factors causing the current rethinking of the peopling of the Americas. However, the New World haplogroup X2a is as different from any of the Old World X2b, X2c, X2d, X2e and X2f lineages as they are from each other, indicating an early origin "likely at the very beginning of their expansion and spread from the Near East".[4]

The Solutrean Hypothesis posits that haplogroup X reached North America with a wave of European migration about 20,000 BP by the Solutreans,[citation needed] a stone-age culture in south-western France and in Spain, by boat around the southern edge of the Arctic ice pack.

[edit] Subclades

[edit] Tree

This phylogenetic tree of haplogroup X subclades is based on the paper by Mannis van Oven and Manfred Kayser Updated comprehensive phylogenetic tree of global human mitochondrial DNA variation[1] and subsequent published research.

  • X
    • X1
      • X1a
        • X1a1
      • X1b
    • X2
      • X2a
        • X2a1
          • X2a1a
          • X2a1b
        • X2a2
      • X2b
        • X2b1
        • X2b2
        • X2b3
        • X2b4
      • X2c
        • X2c1
        • X2d
      • X2e
        • X2e1
          • X2e1a
            • X2e1a1
              • X2e1a1a
        • X2e2
      • X2f
      • X2g
      • X2h


[edit] Popular Culture

In his popular book The Seven Daughters of Eve, Bryan Sykes named the originator of this mtDNA haplogroup "Xenia".

[edit] References

  1. ^ a b van Oven, Mannis; Manfred Kayser (13 Oct 2008). "Updated comprehensive phylogenetic tree of global human mitochondrial DNA variation". Human Mutation 30 (2): E386-E394. PMID 18853457 doi:10.1002/humu.20921. http://www3.interscience.wiley.com/journal/121449735/abstract?CRETRY=1&SRETRY=0. Retrieved on 2009-05-20. 
  2. ^ Dolan DNA Learning Center - Native American haplogroups: European lineage, Douglas Wallace
  3. ^ Derenko MV, Grzybowski T, Malyarchuk BA, Czarny J, Miścicka-Sliwka D, Zakharov IA (July 2001). "The presence of mitochondrial haplogroup x in Altaians from South Siberia". Am. J. Hum. Genet. 69 (1): 237–41. doi:10.1086/321266. PMID 11410843. 
  4. ^ a b c Reidla M, Kivisild T, Metspalu E, et al. (November 2003). "Origin and diffusion of mtDNA haplogroup X". Am. J. Hum. Genet. 73 (5): 1178–90. doi:10.1086/379380. PMID 14574647. 

[edit] See also

Human mitochondrial DNA (mtDNA) haplogroups
  most recent common mt-ancestor    
L0 L1 L2 L3   L4 L5 L6 L7
  M N  
CZ D E G Q   A S   R   I W X Y
C Z B F HV   JT P  U
H V J T K Former Clusters IWX

[edit] External links

Retrieved from "http://en.wikipedia.org/wiki/Haplogroup_X_(mtDNA)"
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