Тезисы докладов

Изменчивость генома человека

Haplogroup M is the most frequent mtDNA cluster found among Indian and east Asian populations. M frequency in Central Asia is close to that in India and in eastern Asians. Indian haplogroup M sub-structure differs profoundly from that observed in East Asian populations, where haplogroups D, E, G, C, Z constitute the bulk of M lineages. A number of Indian-specific M lineage clusters can be defined. Indian M is further characterised by relative abundance of lineages arising from the central M node.

The coalescence times of East Asian and Indian haplogroup M lineages have been estimated to be over 50 000 BP. This suggests that the two macro-populations started to expand separately but simultaneously and since then, there has been only very limited gene flow between India and eastern Asia. The lack of any signs for extensive re-migrations of eastern Asians to India is further supported by the scarcity of mtDNA lineages belonging to haplogroups A, B and F in India. Virtually all M lineages found in Central Asian populations belong to the East Asian-specific branches of this haplogroup, suggesting that no large-scale migration from Central Asia to India has occurred.

Geographically, the distribution of haplogroup U is a mirror image of that for haplogroup M: U is not present in eastern Asia, but is frequent in European populations and among Indians. This reverse analogy goes further: Indian U lineages differ substantially from those observed in Europe and their coalescence to a common ancestor, like that for the haplogroup M lineages, dates back to about 50,000 years.

All major West Eurasian-specific mtDNA haplogroups (H, T, J and U) as well as the two major eastern Asian-specific haplogroups B and F derive from a common internal node R. Apart from the defined haplogroups derived from this node, large variety of “non-canonical” derivatives of it (R*) are found in India. Such lineages may be present also east of India, but sadly Myanmar, Thai, Laos etc. are poorly covered, if at all.

Indian tribals, who constitute ~7% of total population of India, often show profound difference in haplogroup frequencies when compared to upper cast populations. Yet, both share the same lineages, though tribals have often lost their diversity. Therefore, bottlenecks or founder-effects in demographic histories and not different origin of the tribals seem to account for the found differences.

The Y-chromosomal haplogroups present in Indians are also frequent in western Eurasians. Though, the opposite is not true. Overlap between the Indian and the south-eastern Asian Y chromosomes is minimal.

Our observations indicate, that when it comes to relating phylogeny to phylogeography, one should not relay too much on marker frequencies, but rather pay attention to the topology of the phylogenetic tree, both in general and in details such as phylogeography of lineages and their sub-clusters.

Примечание. Тезисы докладов публикуются в авторской редакции

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    Дата последней модификации: 06-Jul-2012 (11:44:54)