Genetic variation at three VNTR loci in three tribal populations of Orissa, India

Abstract

Background : The variable number of tandem repeats (VNTR) loci are robust, simple and rapid tools for genetic characterization of both individuals and populations. This paper presents data on the distribution of three VNTRs (APOB, YNZ22 and D1S80) in three tribal populations (Gadaba, Kuvi-Khond and Paroja) of the Koraput district of Orissa, India with a view to enlarge our understanding of molecular genetic diversity among these tribes and the usage of these VNTRs in anthropogenetic studies. Subjects and methods : Three tribal populations were genotyped for APOB, YNZ22 and D1S80 loci using the polymerase chain reaction (PCR) technique. Gadaba are an Austro-Asiatic tribe while Kuvi-Khond and Paroja are Dravidian tribes. All samples were collected, with consent, from unrelated individuals. Results : The observed allelic variation in these tribes is comparable with many Indian populations, but they showed significant overall and inter-population variability within the region. Allele *24 was the most common allele at the D1S80 locus in all populations, with Gadabas having the highest frequency (50%) followed by Paroja (32%) and Kuvi-Khond (23%). Gadabas also showed a higher frequency of allele *19 (13%) and *31 (9%) compared to other Indian and European populations. In the Apo B system, allele *37 was the most common in all three populations, with Gadabas having the highest frequency (39%) followed by Paroja (24%) and Kuvi-Khond (21%). This allele is present in high frequencies in other Indian (except Gonds) and European populations. Alleles *33 (17%), *35 (20%) and *45 (12%) were also common in the Gadabas, but Kuvi-Khond showed higher frequencies of *31(10%), *35(13%) and the larger allele *49(16%). Paroja, on the other hand, had higher frequencies of *31 (14%), *33 (17%) and *45 (13%). Allele *49 was also present in Paroja (10%) but was absent in the Gadaba. For the YNZ22 system, allele *4 was the most common in Kuvi-Khond (25%) and Paroja (21.4%), and allele *2 was the predominant allele in the Gadaba (33%). However allele *4 still occurs at relatively high frequency in Gadaba (27%). Allele *2 also occurs at relatively high frequency in Kuvi-Khond (20%) and intermediate frequency in Paroja (11%). Average heterozygosity was relatively low for Gadaba (0.7597 &#45 0.0191) and high for Kuvi-Khond (0.8618 &#45 0.0149) and Paroja (0.8512 &#45 0.0190), perhaps a reflection of effective population size and limitations to mating. The level of gene differentiation is, however, low (3-4%) for the three systems studied in these tribal populations and in data compiled from previous studies from the region. Conclusions : The VNTRs are polymorphic in the tribal populations studied and there is extensive allelic variation. Gadabas are isolated but Kuvi-Khond and Paroja show clear affinities with the Gonds, a major tribal group of Central India. Overall, allele frequency distribution, heterozygosity and genetic diversity analysis show that genetic diversity observed is socially, linguistically and geographically structured in this region.