Genetic admixture studies on four in situ evolved, two migrant and twenty-one ethnic populations of Tamil Nadu, south India

Abstract

We analysed the genetic structure of ≈ 1000 samples representing 27 ethnic groups settled in Tamil Nadu, south India, derived from two linguistic families (Dravidians and Indo-Europeans) representing four religious groups (Hinduism, Islam, Christianity and Jainism) using 11 mtDNA markers. Out of 27 ethnic groups, four are in situ populations (Anglo-Indian, Labbai Muslim, Nadar Christian and south Indian Jain) and two are migrants (Gypsy and north Indian Jain) from north India to Tamil Nadu, and 21 are native ethnic groups. Six of the markers we used were monomorphic (HaeIII663, HpaI3592, AluI5176, AluI7025, AluI13262, 9-bp deletion) and five markers were polymorphic (DdeI10394, AluI10397, HinfI12308, HincII13259 and HaeIII16517). Haplogroup frequencies, genetic affinities and admixture analysis are based on the genotype data of polymorphic markers observed in these populations. Haplogroup frequencies indicate that various ethnic groups entered Tamil Nadu during different time periods. Genetic affinities and admixture estimates revealed that the ethnic groups possessing advanced knowledge of farming cluster in a branch (C), and could be the late arrived settlers as agriculture, was introduced to this region at about 5 to 3 thousand years ago. In situ ethnic groups appear to have arisen at various times as a result of the prevailing dominant socio-cultural forces. Hierarchical Hindu caste system created many ethnic groups in the history of its existence; some of them became isolated for considerable period of time. Over all, among Tamil ethnic groups, in spite of caste systems' rigidity, built in flexibility in the system in the form of hypergamy and hypogamy had allowed maternal gene flow between them.

Screening for AZFc Partial Deletions in Dravidian Men with Nonobstructive Azoospermia and Oligozoospermia

“…Moreover, the presence of haplogroup N (which is susceptible to partial AZFc deletions) was traced in the Dravidian population with an estimated frequency range of 5% to 42% (Suhasini et al, 2011). In our study, the frequency of b2/b3 subdeletion was higher compared with the related studies (Repping et al, 2004;Eloualid et al, 2012;Rozen et al, 2012).…”

“…Genetic studies on the present day South Indian population revealed that the population itself is an admixture of various racial groups and shows diverse genetic features (Suhasini et al, 2011). Hence, the information received from the genetic screening studies using well-defined case-control samples will serve as useful reference data in relation to the research, diagnosis, and management of male infertility.…”