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Indians are at Higher Risk of Recessive Genetic Diseases

Researchers have found that Indians are a collection of a few genetically isolated groups. Most Indians are the descendants of two major ancestral groups, “the Ancestral North Indians (ANI)” and “the Ancestral South Indians (ASI)”. The rest of the groups formed from the genetic mixture of these two groups. They are named as “founder events”. These groups are found to be genetically isolated because the genes from one group did not pass over to the other group during the past thousands of years.

What the Research Involved

Dr. David Reich of Harvard University and Dr. Lalji Singh of the Center for Cellular and Molecular Biology in India wanted to study the variations of genes in the Indian population. These scientists used DNA samples of 132 people from 15 states of India and represented 25 diverse ethnic groups. The findings were published in the September 24, 2009 issue of the periodical Nature.

This study found that the groups that are seen today have emerged from two ancient populations that have a distinct genetic affinity. Those that emerged from the ANI showed between 40 to 80 percent genetic affinity to the European population. Those populations that emerged from the ASI did not show any affinity to a particular population outside of India. The Hyshi and Ao Nage populations from northeast India showed genetic affinity to the Chinese while the indigenous populations found in the Andamans have more affinity to the ASI.

Significance of these Research Findings

The risks of genetic diseases increase when the genes of a particular group remain within that group. This is due to the fact that the defects present in the genes are acquired by all the descendants of that group. Apparently, when genes from two different groups interact, the chance of the risk of defects is greatly reduced. These research findings suggest that Indians, being from genetically isolated groups, are at high risk for recessive genetic diseases. This is known as the “founder effect”, where shared descent from a common ancestral population plays a greater role in the development of certain diseases. Basically, the founder effect is the fact that many groups seen in India today have descended from a small group of founding individuals and these founding individuals have been isolated from other groups in regards to genetics.

According to Singh, this research has greatly increased our understanding of inherited disorders. In India there are 4,635 anthropologically well-defined populations with little or no gene flow between them. The differences between these groups show geographic, caste, and other cultural barriers to interbreeding. It is now known that genetic variations among these Indian groups are directly related to differences in the distribution and frequency of specific genetic disorders.

Source: nih.gov

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