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In human genetics, Haplogroup R1 is a Y-chromosome DNA haplogroup, a subgroup of haplogroup R, associated with the M173 mutation. It is dominated in practice by two very common Eurasian clades, R1a and R1a, which together are found all over Eurasia except in Southeast Asia and East Asia. However other types of R1, less well-known and defined and therefore referred to collectively simply as R1* or R-M173*, have been found in significant concentrations in Central Africa, Jordan, and Central Asia.
[edit] OriginsThe origins of R1 remain unclear. On the one hand there is a significant presence as far south as Central Africa, for example Cameroon. Although this is generally seen as a result of back migration from Eurasia, it has been seen, especially in conjunction with high levels of R1* in Jordan, as indicative of the likelihood that R1 had origins in the Middle East. On the other hand, R1's sibling clade, R2, is South Asian and generally considered to have originated in or near South Asia. This suggests an origin for R1 to the east of the Middle East. For example, Kivisild et al. (2003) believes the evidence "suggests that southern and western Asia might be the source of this haplogroup".[3] Looking at R1's relatives more generally, haplogroup R is part of the family of haplogroup P, and a sibling clade therefore, of haplogroup Q, which is common in the Americas, and in Eurasia is associated with eastern areas such as Siberia. [edit] DistributionR1 is very common throughout all of Eurasia except East Asia and Southeast Asia. Its distribution is believed to be associated with the re-settlement of Eurasia following the last glacial maximum. Its main subgroups are R1a (M420) and R1b (M343). One subclade of haplogroup R1b (especially R1b1b2, R-M269), is the most common haplogroup in Western Europe, while another R1a (especially R1a1a, R-M17 or R-M98) is the most common haplogroup in Eastern Europe as well as some parts of Central Asia, South Asia, Western China, and South Siberia.[4] One isolated clade (or clades) of Y chromosomes that appear to belong to Haplogroup R1b1* (P25-derived) is found at high frequency among the native populations of northern Cameroon, such as the Kirdi, in west-central Africa, which is believed to reflect a prehistoric back-migration of an ancient proto-Eurasian population into Africa. Individuals whose Y-chromosomes possess all the mutations on internal nodes of the Y-DNA tree down to and including M207 (which defines Haplogroup R) but which display neither the M173 mutation that defines Haplogroup R1 nor the M124 mutation that defines Haplogroup R2 are categorised as belonging to group R*. Haplogroup R* has been found in 10.3% (10/97) of a sample of Burusho and 6.8% (3/44) of a sample of Kalash from northern Pakistan.[5] [edit] SubcladesThe subclades of haplogroup R with their defining mutation, according to the stratification chart published by the 2009 International Society of Genetic Genealogy (ISOGG)[6]:
[edit] R1Haplogroup R1 contains the majority of representatives of haplogroup R in the form of its subclades, R1a and R1b.[7][8][9] [edit] R1aMain article: Haplogroup R1a (Y-DNA) The highest levels of R1a (>50%) are found found in certain populations in Eurasia, from Central Europe to Northern India and Western China: Kashmiri Pandits (72%), the Ishkashimi (68%), the Tajik population of Khojant (64%), Kyrgyz (63.5%), Sorbs (63.39%), Poles (56.4%), and Ukrainians (54.0%)[10][11][12][8] and in the central India among the sahariai tribe of North india (72%).[13] R1a has been variously associated with:
[edit] R1bMain article: Haplogroup R1b (Y-DNA) Haplogroup R1b probably originated in Eurasia prior to or during the last glaciation. It is the most common haplogroup in Western Europe and may have survived the LGM concentrated in refugia in southern Europe and the Aegean. It is also present at lower frequencies throughout Eastern Europe, with higher diversity than in western Europe, suggesting an ancient migration of R1b from the east.[16] R1b is also found at various frequencies in many different populations near the Ural Mountains and Central Asia, its likely region of origin. It is also found in North Africa where its frequency surpasses 10% in some parts of Algeria[17]. In south-eastern England the frequency of R1b is about 70%; in parts of the rest of north and western England, Spain, Portugal, Wales and Ireland, it is as high as 90%; and in parts of north-western Ireland it reaches 98%. The R1b clade appears to have a much higher degree of internal diversity than R1a, which suggests that the M343 mutation that derives R1b from R1* may have occurred considerably earlier than the SRY1532 mutation that defines R1a. R1b (previously called Hg1 and Eu18) is the most frequent Y-chromosome haplogroup in Europe. It is an offshoot of R1 (M173), characterised by the M343 marker.[18] An overwhelming majority of members of R1b are classified as R1b1 (defined by the P25 marker), the remainder as R1b*. Its frequency is highest in Western Europe (and due to modern European emigration, in parts of the Americas). The majority of R1b-carriers of European descent belong to the subclade R1b1b2 (M269). [edit] Notes
[edit] References
[edit] See also
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