Washington: Indians make up one of the major human ancestry groups, with relatively little genetic differentiation among the people from different parts of the country, according to a new US study.

Although the study used participants that may not reflect a random sample from India, these results still suggest that the frequencies of many genetic variants are distinctive in India compared to other parts of the world, an Indian American scientist who led the study said.

"We were struck both by the low level of diversity amongst people spanning such a large geographical region, and by the fact that people of the Indian sub-continent constituted a distinct group when compared to populations from other parts of the world," said Pragna I. Patel.

The study led by Patel, professor of biochemistry and molecular biology at the Keck School of Medicine of the University of Southern California (USC), represents the largest study of Indian genetic variation performed to date, in terms of the total number of sites in the human genome that were surveyed.

Her group is using this study as a foundation for future studies on the genetic basis of various common diseases in Asian Indians - such as heart disease, which is highly prevalent in this population.

For their study, Patel and Noah Rosenberg, assistant professor in the department of Human Genetics at the University of Michigan, conducted genetic analysis of Indian-born individuals in the US. Their studies of 1,200 genome-wide polymorphisms collected from 432 individuals representing 15 different Indian populations, have begun to shed light on the genetic variations of the diverse population of India.

Patel took up the project as despite the fact that the people of India constitute more than one-sixth of the world's entire population, they have been underrepresented in studies related to genetic diseases.

And with the growth of modernisation, complex genetic diseases associated with urban and western lifestyles have risen to near-epidemic proportions, making genetic cataloguing and association studies of particular importance.

The research group also includes other researchers from the USC Institute for Genetic Medicine at the Keck School of Medicine, the University of Michigan, the departments of neurology and molecular and human genetics at Baylor College of Medicine in Houston, Texas, and the Centre for Medical Genetics at the Marshfield Medical Research Foundation, Marshfield, Wisconsin.

The study was funded by a Burroughs Wellcome Fund Career Award in the Biomedical Sciences (Rosenberg), an Alfred P. Sloan Research Fellowship (Rosenberg) and a grant from the University of Southern California. The National Heart, Lung and Blood Institute provided additional support for genotyping.