If the genetic study of 275,000 pure-bred residents of Iceland could lead to the discovery of disease patterns and new drugs, India can offer a better opportunity, argues Lalji Singh, director of the Centre for Cellular and Molecular Biology in Hyderabad.
With its 4,635 anthropologically well-defined endogamous populations-- of which 532 are tribal, including 72 primitive populations, India is a bigger laboratory than Iceland to study population/community-based genetic diseases, says Kumarasamy Thangaraj, scientist at CCMB.
Singh and Thangaraj, along with other scientists S Deepa, A Vanniarajan and A G Reddy are studying the origin and disease susceptibility of various caste and tribal populations of India.
CCMB scientists hope to find in the tribes' gene pool tiny genetic mutations that can cause diseases. It is relatively easier to isolate genes and pick out anomalies, including diseased genes, in a homogenous group where the gene maps of individuals are similar than from a more varied population, such as in the United States.
Some biotech companies like Bangalore-based Biocon see an opportunity in this area of research. Biocon chairperson Kiran Mazumdar-Shaw argues the country's unique gene pools are "gold mines."
The CCMB, in collaboration with the Anthropological Survey of India and various universities has already created a large repository of over 9,000 DNA samples from 130 endogamous populations covering the whole of India.
The sample size is growing. "About 50 million individuals are affected with genetic diseases in India," says Thangaraj.
"Information collected during sample collection has helped us in identifying genetic diseases, which are highly prevalent in particular populations," he said. "It was astonishing that in several populations, the load due to genetic diseases is so high that it is leading to their extinction."
One such tribe is the primitive Onges of Andaman and Nicobar Islands. Their number has reduced from 700 in 1858 to 98 now.
Genetic analysis of the DNA of 46 of them by the CCMB team revealed that the tribe is exposed to double jeopardy.
"We found not only 23 novel mutations in mitochondrial genome linked to genetic diseases but also deletion, in male samples, of certain genes in Y chromosome responsible for sperm production," Thangaraj said.
The occurrence of deletion in different regions of the Y chromosome in the 23 male samples analysed suggest that deletion events causing infertility keep accumulating. Thangaraj says the study strongly suggests a genetic basis behind the dwindling population of Onges.
