Tag Archive for 'Genome'

Genomes link aboriginal Australians to Indians

Ed Yong in Nature:

Some aboriginal Australians can trace as much as 11% of their genomes to migrants who reached the island around 4,000 years ago from India, a study suggests. Along with their genes, the migrants brought different tool-making techniques and the ancestors of the dingo, researchers say.

This scenario is the result of a large genetic analysis outlined today in the Proceedings of the National Academy of Sciences. It contradicts a commonly held view that Australia had no contact with the rest of the world between the arrival of the first humans around 45,000 years ago and the coming of Europeans in the eighteenth century.

“Australia is thought to represent one of the earliest migrations for humans after they left Africa, but it seemed pretty isolated after that,” says Mark Stoneking, a geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who led the study. More:

Parsi genome sequenced

From The Times of India:

For the first time, scientists have sequenced the entire genome of a Parsi woman (74) suffering from an heritable form of breast cancer.

Researchers say, the exercise will help in finding variations in DNA. Once matched with DNA of other communities, they will know if these changes in DNA are unique to Parsis and are associated with the disease.

The finding will lead to proper diagnosis and help the Parsis — a fast depleting community — not to be susceptible to it.

The exercise is a part of “Avestagenome Project” — a study on the Parsis to determine the genetic basis of their longevity and age-related disorders.

Speaking to TOI, Dr Sami Guzder, head of science and innovation division at Avesthagen — a Bangalore-based biotechnology company — said, “we will know in two months that variations is possibly causing this spike in breast cancer cases among the Parsis.” More:

In Tibetans, evidence of “fastest case of human evolution”

Nicholas Wade in The New York Times:

Tibetans live at altitudes of 13,000 feet, breathing air that has 40 percent less oxygen than is available at sea level, yet suffer very little mountain sickness. The reason, according to a team of biologists in China, is human evolution, in what may be the most recent and fastest instance detected so far.

Comparing the genomes of Tibetans and Han Chinese, the majority ethnic group in China, the biologists found that at least 30 genes had undergone evolutionary change in the Tibetans as they adapted to life on the high plateau. Tibetans and Han Chinese split apart as recently as 3,000 years ago, say the biologists, a group at the Beijing Genomics Institute led by Xin Yi and Jian Wang. The report appears in Friday’s issue of Science.

If confirmed, this would be the most recent known example of human evolutionary change. Until now, the most recent such change was the spread of lactose tolerance — the ability to digest milk in adulthood — among northern Europeans about 7,500 years ago. But archaeologists say that the Tibetan plateau was inhabited much earlier than 3,000 years ago and that the geneticists’ date is incorrect.

When lowlanders try to live at high altitudes, their blood thickens as the body tries to counteract the low oxygen levels by churning out more red blood cells. This overproduction of red blood cells leads to chronic mountain sickness and to lesser fertility — Han Chinese living in Tibet have three times the infant mortality of Tibetans. More:

Indian ancestry revealed

From Nature:

Now, a team led by David Reich of the Broad Institute in Cambridge, Massachusetts, and Lalji Singh of the Centre for Cellular and Molecular Biology in Hyderabad, India, has probed more than 560,000 SNPs across the genomes of 132 Indian individuals from 25 diverse ethnic and tribal groups dotted all over India.

The researchers showed that most Indian populations are genetic admixtures of two ancient, genetically divergent groups, which each contributed around 40-60% of the DNA to most present-day populations. One ancestral lineage – which is genetically similar to Middle Eastern, Central Asian and European populations – was higher in upper-caste individuals and speakers of Indo-European languages such as Hindi, the researchers found. The other lineage was not close to any group outside the subcontinent, and was most common in people indigenous to the Andaman Islands, a remote archipelago in the Bay of Bengal. More:

caste_chart

Reconstructing Indian population history

The abstract in Nature:

India has been underrepresented in genome-wide surveys of human variation. We analyse 25 diverse groups in India to provide strong evidence for two ancient populations, genetically divergent, that are ancestral to most Indians today. One, the ‘Ancestral North Indians’ (ANI), is genetically close to Middle Easterners, Central Asians, and Europeans, whereas the other, the ‘Ancestral South Indians’ (ASI), is as distinct from ANI and East Asians as they are from each other. By introducing methods that can estimate ancestry without accurate ancestral populations, we show that ANI ancestry ranges from 39-71% in most Indian groups, and is higher in traditionally upper caste and Indo-European speakers. Groups with only ASI ancestry may no longer exist in mainland India. However, the indigenous Andaman Islanders are unique in being ASI-related groups without ANI ancestry.

And read Indians as hybrids: Razib Khan at ScienceBlogs:

study

Read Aryan-Dravidian divide a myth in the Times of India.