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)

Comments

Popular posts from this blog

NGT terminates chairmen of pollution control boards in 10 states (downtoearth,)

Cracking the whip on 10 State Pollution Control Boards (SPCBs) for ad-hoc appointments, the National Green Tribunal has ordered the termination of Chairpersons of these regulatory authorities. The concerned states are Himachal Pradesh, Sikkim, Tamil Nadu, Uttarakhand, Kerala, Rajasthan, Telangana, Haryana, Maharashtra and Manipur. The order was given last week by the principal bench of the NGT, chaired by Justice Swatanter Kumar. The recent order of June 8, 2017, comes as a follow-up to an NGT judgment given in August 2016. In that judgment, the NGT had issued directions on appointments of Chairmen and Member Secretaries of the SPCBs, emphasising on crucial roles they have in pollution control and abatement. It then specified required qualifications as well as tenure of the authorities. States were required to act on the orders within three months and frame Rules for appointment [See Box: Highlights of the NGT judgment of 2016 on criteria for SPCB chairperson appointment]. Having

High dose of Vitamin C and B3 can kill colon cancer cells: study (downtoearth)

In a first, a team of researchers has found that high doses of Vitamin C and niacin or Vitamin B3 can kill cancer stem cells. A study published in Cell Biology International showed the opposing effects of low and high dose of vitamin C and vitamin B3 on colon cancer stem cells. Led by Bipasha Bose and Sudheer Shenoy, the team found that while low doses (5-25 micromolar) of Vitamin C and B3 proliferate colon cancer stem cells, high doses (100 to 1,000 micromolar) killed cancer stem cells. Such high doses of vitamins can only be achieved through intravenous injections in colon cancer patients. The third leading cause of cancer deaths worldwide, colon cancer can be prevented by an intake of dietary fibre and lifestyle changes. While the next step of the researchers is to delineate the mechanisms involved in such opposing effects, they also hope to establish a therapeutic dose of Vitamin C and B3 for colon cancer stem cell therapy. “If the therapeutic dose gets validated under in vivo

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 i