All People With Blue Eyes Have A Single, Common Ancestor

Calendar October 10, 2022 | Posted by admin

According to the Cleveland Clinic, up until some 10,000 years ago, it’s believed everyone in the world had brown eyes. Now, an estimated 8-10% of people in the world have blue eyes. How did that come to be? As it turns out, researchers now believe blue eyes all started with a single person who passed on a genetic mutation that spread across the world. In other words, everyone with blue eyes shares a single, common ancestor.

Back in 2008, researchers with the University of Copenhagen examined the exact genetic mutation that resulted in blue eyes all those years ago. Their research was published in the The Journal of Human Genetics. According to Science Daily, the study’s lead author, Professor Hans Eiberg, explained that humans originally had brown eyes, and a gene mutation “turned off” the ability to produce brown eyes – resulting in some people having blue eyes. The press release elaborated that the affected gene, the OCA2 gene, regulates brown pigment in the eyes. If the OCA2 gene had been completely destroyed or “turned off” then the affected humans would be without any melanin in their hair, eyes, or skin color (a condition known as albinism). But with the specific mutation, the body has a limited ability to produce melanin in the iris, resulting in a blue iris, rather than a brown iris. The genetic mutation isn’t a positive or negative trait.

“Mutations can affect things like freckles, balding patterns, hair color, and more“. “It simply shows that nature is constantly shuffling the human genome, creating a genetic cocktail of human chromosomes and trying out different changes as it does so,” explained Eiberg.

According to the College of Physicians of Philadelphia, researchers studied the mitochondrial DNA of individuals with blue eyes from various countries, such as Jordan, Denmark, and Turkey. The researchers found that over 97% of the blue-eyed people in the study shared a single haplotype – a grouping of genomic variants that are usually inherited. Because of this, researchers believe that the mutation is passed on genetically, meaning that everyone with blue eyes is related.

“From this, we can conclude that all blue-eyed individuals are linked to the same ancestor. They inherited the same switch at the same spot in their DNA,” said Eidberg in a press release, shared in EurekaAlerta!,

Source: https://blog.thebreastcancersite.greatergood.com

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Rare genetic mutation holds clues to preventing Alzheimer’s

Calendar November 7, 2019 | Posted by admin

Could one woman’s rare genetic mutation one day have a global impact on dementia risk? It’s possible, say investigators who report on a potentially groundbreaking case of a woman whose genetic mutation staved off dementia for decades, even though her brain had already been damaged by Alzheimer’s disease. While most Alzheimer’s cases are not driven by genetic predisposition, one woman in Colombia is among about 1,200 in her country who do face a genetically higher risk for early-onset Alzheimer’s. Why? They all carry the E280A mutation of a gene called Presenilin 1 (PSEN1), which is known to increase the chances for Alzheimer’s at a far younger age than usual.

“We identified an individual that was predisposed to develop Alzheimer’s in her 40s,” noted study author Dr. Joseph Arboleda-Velasquez. He’s an assistant professor of ophthalmology with the Schepens Eye Research Institute of Mass Eye and Ear at Harvard Medical School, in Boston.

But, strangely, the woman “remained unimpaired until her 70s,” Arboleda-Velasquez added. The twist: the woman had, in fact, developed clear telltale signs of Alzheimer’s in her brain. She just hadn’t developed dementia. For example, while she had fewer neural “tangles” in her brain than is typical for Alzheimer’s patients, by the time she hit her 40s she did have the same unusually high level of brain amyloid-beta deposits as her E280A peers. Such deposits are a key signature of Alzheimer’s. So why didn’t she develop middle-aged dementia like her peers?

To unravel the mystery, Arboleda-Velasquez and his colleagues ran an in-depth genetic analysis on the woman. And what they found is that she had not just one mutation, but two. In addition to the E280A mutation, she also carried the so-called “Christchurch” mutation in the APOE3 gene. But there’s more. Not only did she carry the Christchurch mutation, but she had two of them. Some of her E280A peers (about 6%) also carried a single copy of Christchurch. But she was the only one who carried two, the investigators found. “It is ultra-rare, with an approximate prevalence of less than one in every 200,000 individuals,” Arboleda-Velasquez said.

And having one such rare mutation did not appear to be enough. No protection against dementia was linked to only one Christchurch mutation. But as this woman’s case suggests, having two such mutations did seem to throw up a shield against Alzheimer’s, preserving her ability to remember things and think clearly for a few decades, long after her E280A peers had started experiencing cognitive decline.

Source: https://www.cbsnews.com/

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How To Detect Genetic Mutations In Minutes

Calendar March 28, 2019 | Posted by admin

A team of engineers at the UC Berkeley and the Keck Graduate Institute (KGI) of The Claremont Colleges combined CRISPR with electronic transistors made from graphene to create a new hand-held device that can detect specific genetic mutations in a matter of minutes.

The device, dubbed CRISPR-Chip, could be used to rapidly diagnose genetic diseases or to evaluate the accuracy of gene-editing techniques. The team used the device to identify genetic mutations in DNA samples from Duchenne muscular dystrophy patients.

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“We have developed the first transistor that uses CRISPR to search your genome for potential mutations,” said Kiana Aran, an assistant professor at KGI who conceived of the technology while a postdoctoral scholar in UC Berkeley bioengineering professor Irina Conboy’s lab. “You just put your purified DNA sample on the chip, allow CRISPR to do the search and the graphene transistor reports the result of this search in minutes.”

Aran, who developed this technology and brought it to fruition at KGI, is the senior author of a paper describing the device that appears online March 25 in the journal Nature Biomedical Engineering.

Doctors and geneticists can now sequence DNA to pinpoint genetic mutations underlying a host of traits and conditions, and companies like 23andMe and AncestryDNA even make these tests available to curious consumers.

Source: https://news.berkeley.edu/

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‘Epigenetic’ Gene Tweaks Could Trigger Cancer

Calendar March 7, 2019 | Posted by admin

You could be forgiven for thinking of cancer as a genetic disease. Sure, we know it can be triggered by things you do – smoking being the classic example – but most of us probably assume that we get cancer because of a genetic mutation – a glitch in our DNA. It turns out that this is not quite the end of the story.

We now have the first direct evidence that switching off certain genes – something that can be caused by our lifestyle or the environment we live in – can trigger tumours, without mutating the DNA itself. The good news is that these changes are, in theory, reversible.

All cells contain the same DNA, but individual genes in any cell can be switched on or off by the addition or subtraction of a methyl group – a process known as epigenetic methylation.

For years, researchers have known that mutations to our DNA – either those passed on at birth or those acquired as a result of exposure to radiation, for example – can cause cancer. But epigenetic changes have also been implicated in cancer because abnormal patterns of gene methylation are seen in virtually all types of human tumours.

For example, a gene called MLH1 produces a protein that repairs DNA damage. It is often mutated in colon cancer tumours, but in some tumour samples the gene is healthy, but appears to have been silenced by methylation. The problem is that it has been difficult to test whether abnormal methylation occurs as a result of a tumour or is a cause of its growth.

“In genetics you can easily delete a gene and see what the consequence is, but it’s much harder to direct methylation to specific regions of the genome,” says Lanlan Shen of Baylor College of Medicine in Houston, Texas.

To get round this problem, Shen and her colleagues used a naturally occurring sequence of DNA, which draws in methyl groups to methylate nearby genes. They call it their “methylation magnet”.

The team inserted this sequence next to the tumour suppressor gene, p16, in mouse embryonic stem cells. These embryos then developed into mice that carry the “methylation magnet” in all of their cells. The team focused on methylating p16 because it is abnormally methylated in numerous cancers.

They monitored the rodents for 18 months – until they reached the mouse equivalent of middle age. Over this time, 30 per cent of the mice developed tumours around their body, including in their liver, colon, lungs and spleen. None of a control group of genetically identical mice developed tumours.

“Some tissues showed faster methylation than others, for example in the liver, colon and spleen, and that’s exactly where we saw the tumours grow,” says Shen. “It seems like methylation predisposed the tissue to tumour development.” She reckons that methylation silences p16, which lifts the break that it normally places on any abnormal cell division.

Source: https://www.newscientist.com/

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