Skip to main content

n caste-ridden India, genetic isolation may be harmful to health (downtoearth)

The occurrence of genetic diseases in certain subpopulations in India and other countries in South Asia is well known. Indian scientists now suspect that this could be due to genetic isolation caused by endogamous marriages over generations.

Endogamous marriages—meaning people marrying within a subpopulation based on caste, gotra, language or culture—lead to reduced genetic variation. They are different from marriages among close relatives (consanguineous marriages), a practice also prevalent in parts of South India.

In genetics, the phenomenon of a small number of ancestors giving rise to many descendants is known as “founder event” or a population bottleneck. A study of anthropologically different subpopulations in South Asia has revealed that many of them are a result of strong ‘founder events’. In each of such groups, large stretches of DNA originates from a common founder in the last about 100 generations.

There is less genetic variation because these subpopulations have lived in genetic isolation despite co-living with other groups for centuries due to various factors including caste. Such populations are vulnerable to recessive genetic diseases (in which an offspring gets disease-causing genes from both parents). This risk, researchers say, is very different from that due to marriages among close relatives.

The study, led by scientists at Hyderabad-based Centre for Cellular and Molecular Biology (CCMB), appeared in scientific journal Nature Genetics on Tuesday. Scientists analysed samples from over 2800 individuals from over 275 distinct South Asian populations belonging to various social and linguistic groups from India, Pakistan, Nepal, Sri Lanka, and Bangladesh. They developed an algorithm to quantify impact of ‘founder events’ in each group based on stretches in DNA shared from a common founder over generations.

“We found that 81 out of 263 unique South Asian groups, including 14 groups with estimated census sizes of over a million, have a strong founder event,” said Kumarasamy Thangaraj, who led the study along with David Reich of Harvard Medical School.  These large population groups with founder events include Gujjar (Jammu & Kashmir), Baniyas (UP), Pattapu kapu (AP), Vadde (AP), Yadav (Puducherry), Kashtriya Aqnikula (AP), Naga (Nagaland), Kumhar (UP), Reddy (Telangana), Kallar (TN), Brahmin Manipuri (Manipur), Arunthathiyar (TN) and Vysya (Telangana).

Researchers have highlighted the problem through example of Vysya population which has size of more than 3 million. The Vysyas have about 100-fold higher rate of a metabolic disorder called Butyrylcholinesterase (BChE) deficiency compared to other groups. Such people are highly sensitive to anesthesia administered prior to surgery.

“The next step would be to identify specific recessive diseases among various subpopulations and identify genes responsible for them,” Dr Thangaraj told India Science Wire. The research can have significant public health applications, as has been done with some population groups like Ashkenazi Jews, Finns, Amish, Hutterites, Sardinians, and French Canadians in the West. Once recessive genetic diseases specific to different groups are mapped, preventive steps like prenatal testing, premarital counseling and screening can help decrease burden of such diseases in communities.

The team of researchers came from Columbia University; Broad Institute of Harvard and Massachusetts Institute of Technology; Manipal University; Centre for Human Genetics, Bangalore; Mangalore University; Fetal Care Research Foundation, Chennai; Amity University, Noida; Genome Foundation, Hyderabad; Anthropological Survey of India, Kolkata; and Birbal Sahani Institute of Paliosciences, Lucknow. The research was funded by Department of Science and Technology (DST), Department of Biotechnology (DBT), Indian Council of Medical Research (ICMR). (India Science Wire)


Popular posts from this blog

Cloud seeding

Demonstrating the function of the flare rack that carries silver iodide for cloud-seeding through an aircraft. 
Water is essential for life on the earth. Precipitation from the skies is the only source for it. India and the rest of Asia are dependent on the monsoons for rains. While the South West Monsoon is the main source for India as a whole, Tamil Nadu and coastal areas of South Andhra Pradesh get the benefit of the North East Monsoon, which is just a less dependable beat on the reversal of the South West Monsoon winds.

SC asks Centre to strike a balance on Rohingya issue (.hindu)

Supreme Court orally indicates that the government should not deport Rohingya “now” as the Centre prevails over it to not record any such views in its formal order, citing “international ramifications”.

The Supreme Court on Friday came close to ordering the government not to deport the Rohingya.

It finally settled on merely observing that a balance should be struck between humanitarian concern for the community and the country's national security and economic interests.

The court was hearing a bunch of petitions, one filed by persons within the Rohingya community, against a proposed move to deport over 40,000 Rohingya refugees. A three-judge Bench, led by Chief Justice of India Dipak Misra, began by orally indicating that the government should not deport Rohingya “now”, but the government prevailed on the court to not pass any formal order, citing “international ramifications”. With this, the status quo continues even though the court gave the community liberty to approach it in …

India’s criminal wastage: over 10 million works under MGNREGA incomplete or abandoned (hindu)

In the last three and half years, the rate of work completion under the Mahatma Gandhi National Rural Employment Guarantee Act (MGNREGA) has drastically declined, leading to wastage of public money and leaving villages more prone to drought. This could also be a reason for people moving out of the programme.

At a time when more than one-third of India’s districts are reeling under a drought-like situation due to deficit rainfall, here comes another bad news. The works started under the MGNREGA—close to 80 per cent related to water conservation, irrigation and land development—are increasingly not being completed or in practice, abandoned.

Going by the data (as on October 12) in the Ministry of Rural Development’s website, which tracks progress of MGNREGA through a comprehensive MIS, 10.4 million works have not been completed since April 2014. In the last three and half years, 39.7 million works were started under the programme. Going by the stipulation under the programme, close to 7…