Where chromosomes agree, researchers find signatures of human migrations and marriage practices
Stanford researchers have helped find a way to tease out the stretches of genome that are shared among affected individuals due to a recent common ancestor.
(Medical Xpress) -- Your genome is a window onto your heritage or, more precisely, several windows. There are the marks left by human evolution, the traces of ancient human migrations out of Africa and, scattered throughout, clues to your immediate ancestors' marriage habits.
This last detail is particularly interesting to medical geneticists. They're looking for the genes underlying rare, recessive diseases that mainly crop up in populations with a high number of marriages among close relatives, known as consanguineous marriages.
But this can be like looking for a needle in a haystack. Teasing out the stretches of genome that are shared among affected individuals due to a recent common ancestor, rather than from vestiges of deep population history, would significantly reduce the amount of hay.
A group of researchers, led by Stanford biology research associate Trevor Pemberton and biology Associate Professor Noah Rosenberg, has developed a way to attempt to do just that, laying bare worldwide genome patterns in the process.
The research paper, authored with Stanford biology Professor Marcus Feldman, Devin Absher and Richard Myers of the HudsonAlpha Institute for Biotechnology, and Jun Li of the University of Michigan, appeared Thursday in the American Journal of Human Genetics.
Runs of homozygosity, or ROH, are segments of the genome where both chromosomes are identical. Homozygosity is what allows recessive traits, like blue eyes or cystic fibrosis, to appear at all otherwise, the presence of a single dominant counterpart for a gene would mask the recessive characteristic.
Researchers have considered ROH before, but this comprehensive study of nearly 2,000 individuals from 64 populations across the world took a different approach. Using a new statistical model, the researchers "can disentangle ROH that are due to ancient population history from those that are due to recent consanguineous marriages," said Pemberton.
There are three flavors of ROH, separated by length. These all "follow different patterns," Pemberton explained, "which is what you'd expect when there are different processes underlying each of them."
Short- and middling-length ROH both vary with geography. Not only do they show distinct patterns on different continents, they increase in number as you move farther away from East Africa. It's a clear artifact of ancient waves of human migration.
"It's something novel, to see the signature of the distance from Africa in the ROH by separating them into classes of different size," Rosenberg said.
Africa, accordingly, also has the most diverse array of these short and intermediate ROH, while more recently populated regions such as Oceania and the Americas have the fewest.
These runs hearken back to events that are tens of thousands of years old. And many of the short runs the more ancient of the two appear to be fragments of even older ROH.
The longest ROH, however, follow a different pattern. Younger and rarer, these runs don't obey a simple out-of-Africa progression. Instead, they appear most often in societies that have a history of marriage between relatives in the Middle East and Central and South Asia, in particular. Adherence to the caste system in certain Indian towns, for instance, can severely limit spouse options.
These newer runs are also the ones that may help researchers narrow in on the chromosomal regions harboring the genes behind rare, recessive conditions typically a side effect of relatively recent consanguineous marriage.
Researchers should be able to compare the ROH of an individual with a disease to those same chromosomal stretches in unaffected members of the same population group. "If it's frequently homozygous in the general population, you can largely discount the chromosomal region as a candidate," said Pemberton. "If it's rarely homozygous in the general population, it becomes a stronger candidate."
The group has already begun tentative collaborations with medical geneticists and has released a genomic map of the ROH locations.
"The idea is, the resource will be there and available for anyone who wants to come in and answer a question," Rosenberg said.
More information: To read full paper: www.cell.com/AJHG/… 12%2900323-0
Journal reference: American Journal of Human Genetics
Provided by Stanford University
- New algorithm provides new insights into evolutionary exodus out of Africa Jul 13, 2011 | not rated yet | 0
- Continents influenced human migration, spread of technology Sep 19, 2011 | not rated yet | 0
- The peopling of the Americas: Genetic ancestry influences health Aug 14, 2009 | not rated yet | 0
- The role of inbreeding in the extinction of the Spanish Habsburg dynasty Apr 15, 2009 | not rated yet | 0
- Why not marry your cousin? Millions do Apr 25, 2012 | not rated yet | 0
- Motion perception revisited: High Phi effect challenges established motion perception assumptions Apr 23, 2013 | 3 / 5 (2) | 2
- Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update) Apr 02, 2013 | 4.5 / 5 (11) | 5
- The visual system as economist: Neural resource allocation in visual adaptation Mar 30, 2013 | 5 / 5 (2) | 9
- Separate lives: Neuronal and organismal lifespans decoupled Mar 27, 2013 | 4.9 / 5 (8) | 0
- Sizing things up: The evolutionary neurobiology of scale invariance Feb 28, 2013 | 4.8 / 5 (10) | 14
Classical and Quantum Mechanics via Lie algebras
Apr 15, 2011 I'd like to open a discussion thread for version 2 of the draft of my book ''Classical and Quantum Mechanics via Lie algebras'', available online at http://lanl.arxiv.org/abs/0810.1019 , and for the...
- More from Physics Forums - Independent Research
More news stories
Northwestern University scientists have shown a gene involved in neurodegenerative disease also plays a critical role in the proper function of the circadian clock.
Genetics May 16, 2013 | not rated yet | 0 |
Informed consent is the backbone of patient care. Genetic testing has long required patient consent and patients have had a "right not to know" the results. However, as 21st century medicine now begins to use the tools of ...
Genetics May 16, 2013 | 5 / 5 (1) | 3 |
Ethicists provide framework supporting new recommendations on reporting incidental findings in gene sequencing
In a paper published in Science Express, a group of experts led by bioethicists in the Center for Medical Ethics and Health Policy at Baylor College of Medicine provide a framework for the new American College of Medical Geneti ...
Genetics May 16, 2013 | not rated yet | 0
The use of genome-wide analysis (GWA), where the entirety of an individual's DNA is examined to look for the genomic mutations or variants which can cause health problems is a massively useful technology for diagnosing disease. ...
Genetics May 16, 2013 | not rated yet | 0
DNA databases might help identify victims of crime and human trafficking, but how do we safeguard the personal privacy of innocent victims and family members? A new report online May 15 in the Cell Press journal Trends in ...
Genetics May 15, 2013 | not rated yet | 0
A new case of the deadly coronavirus has been detected in Saudi Arabia where 15 people have already died after contracting it, the health ministry announced on Saturday on its Internet website.
14 minutes ago | not rated yet | 0
An increasing number of U.S. children are experiencing gastrointestinal issues that require interventions to resolve, according to research presented at Digestive Disease Week (DDW).
2 hours ago | not rated yet | 0 |
A ground-breaking advance in colonoscopy technology signals the future of colorectal care, according to research presented today at Digestive Disease Week(DDW). Additional research focuses on optimizing the minimal withdrawal ...
2 hours ago | 5 / 5 (1) | 0
Big names in medicine are set to give an upbeat assessment of the war on AIDS on Tuesday, 30 years after French researchers identified the virus that causes the disease.
10 hours ago | 5 / 5 (1) | 0
For combat veterans suffering from post-traumatic stress disorder, 'fear circuitry' in the brain never rests
Chronic trauma can inflict lasting damage to brain regions associated with fear and anxiety. Previous imaging studies of people with post-traumatic stress disorder, or PTSD, have shown that these brain regions can over-or ...
11 hours ago | 5 / 5 (1) | 0 |
(Medical Xpress)—What if the quality of your work depends more on your focus on the piano keys or canvas or laptop than your musical or painting or computing skills? If target users can be convinced, they ...
23 hours ago | 3.7 / 5 (3) | 0 |