A gene variant known to increase the risk of breast and ovarian cancer has been identified in people with Orkney heritage.
New research suggests that one in 100 people with grandparents from Orkney have a specific mutation in the BRCA1 gene.
It found that most of them could trace their ancestry to the Isle of Westray.
This is believed to be the first time such a geographical ancestry link has been made in the UK.
Researchers also found lower levels of a particular Orkney gene variant in genetic testing in the UK and even the US.
Previous studies have shown that women from certain ethnic backgrounds, such as Ashkenazi Jews, also have high levels of a particular BRCA gene variant.
In the UK, around 1 in 1,000 people have the BRCA1 mutation, which can put women at greater risk of ovarian and breast cancer.
BRCA genes are present in every person, both men and women, but if one of them becomes faulty, it can lead to DNA damage and lead to cell cancer.
People with the genetic variant have a 50 percent chance of passing it on to their children.
Awareness of the faulty gene rose ten years ago when Hollywood actress Angelina Jolie underwent double mastectomy after discovering she had the BRCA1 variant.
The surgery was said to reduce her chance of developing breast cancer from 87% to 5%.
However, the NHS advises that risk-reducing surgery is not the only option.
It also advises awareness of breast changes, annual breast screenings and MRI scans can help detect breast cancer, while lifestyle changes such as a healthy diet and exercise can “sometimes reduce the risk”.
There is currently no reliable screening test for ovarian cancer, it adds.
Analysis: Laura Goodwin, BBC Scotland Science and Innovation Correspondent
The identification of this variant – BRCA1 V1736A – is the result of 25 years of clinical research by Prof Zosia Miedzybrodzka, Head of NHS Grampian Clinical Genetics.
At that time, the breast cancer screening center began to notice an increase in the number of families and wanted to know why.
As genetic testing grew, the team saw the same gene variant appear again and again and began to question its significance.
Talking to patients about their ancestry helped create a connection to Westray, an outer Orkney island with a population of just 600.
BRCA1 V1736A is likely to have originated in a founding individual of Westray at least 250 years ago.
To date, 37 women of Orcadian heritage have been identified as carrying the variant.
Some never develop cancer, but others have opted for surgery to reduce the risk.
20 people have been found with the gene variant who do not yet know they carry it.
They were among more than 2,000 volunteers who provided genetic information to the Orcades (Orkney Complex Disease Study).
The design of the study at the time meant that the information was not made public.
The team behind it have now asked the research ethics committee for permission to contact the identified women to tell them they have the BRCA1 gene variant.
Professor Jim Wilson of the University of Edinburgh, who led the research, said: “In humans here on the island hundreds of years ago, this variation occurred in the BRCA 1 gene and now we are finding many descendants both in Westray and further afield. Scotland and beyond.
“I think this is the most significant thing I’ve ever really discovered. It’s going to be of immediate benefit to society as a whole.”
“It’s important that we know”
Former nurse Linda Hagan was born in Westray and has lived there most of her life.
His parents and grandparents and most of his ancestors were also from the island.
Linda, 69, told the BBC that her younger sister died of breast cancer four years ago.
He should get the results of his genetic test soon.
Linda has three daughters and said it would be hard to think of her passing the gene variant on to them.
“But it’s important that we know and hopefully something can be done about it,” he said.
Grandparents from Westray
The latest research from the Universities of Aberdeen and Edinburgh was published in the European Journal of Human Genetics.
The study looked at 80 grandparents of BRCA1 variant carriers identified in the Orcades genetic survey and found that 60% were from Westray.
Other ancestral ties to the island stretched back to the early 18th century.
Orkney has a population of just 22,000, but there are people around the world who share the ancestry and researchers said they should be offered a targeted test for the variant.
Currently in Scotland, the test is available to those who know of a direct family link to the gene or have a family history of ovarian or breast cancer.
A small pilot trial is currently being planned to offer testing to anyone living in Westray who has a Westray-born grandparent, regardless of family history.
If the pilot is successful, the long-term aim is to offer the test to anyone living in Scotland with a Westray-born grandparent who wants it.
NHS Grampian Genetics Clinic runs a helpline on gene variants linked to breast and ovarian cancer for those with grandparents from Orkney. The number to call is 01224 553940. Email inquiries can be directed to gram.orkBRCAgene@nhs.scot
General practitioners cannot help with genetic testing, and all questions about this study and the next steps should be directed to the helpline.