It was their genetic path which led three sisters from Glasgow to their darkest days. Not only did they see their mother die from breast cancer, but each of them, too, has been affected by the disease.

But today Sue Faber, 45, Elaine Mishkin, 43, and Karen Rosen, 37, will take their first steps on the next leg of their emotional journey. They will set off on the West Highland Way to celebrate overcoming illness and surgery and also to raise £25,000 for a University of Glasgow research project which hopes to develop a breast cancer vaccine.

All three sisters inherited the BRCA1 gene mutation and, as Ashkenazi Jewish women, this tiny strand of DNA leaves them with an 85% chance of contracting breast cancer. It took the life of their mother, Lorna Klineberg, when she was just 47.

Karen Rosen was diagnosed when she was only 35 - two months after the birth of her second child. Elaine Mishkin and Sue Faber found out they too carried the deadly mutation and opted to have their breasts removed in a bid to escape the disease.

Standing on the West Highland Way in the miserable driving rain yesterday, the three sisters were clear why they wanted to do the 95-mile walk from Milngavie to Fort William. Elaine has travelled from her home in Mexico City for the event, Karen from New Jersey.

Sue, who lives in Newton Mearns, where all three were brought up, said: "Breast cancer has been so much a part of all of our lives. I think we are just so happy that we are all here, and that Karen is doing so well, we wanted to give something back.

"We think mum would have been so proud of us all; she would have been the first to be cheering us on. I think it will be an emotional journey, particularly at the end. We will have made it through so much together."

The BRCA1 gene may have been a terrifying threat for the women, but knowledge on its existence has also, in some ways, allowed for their survival.

Sue tested positive for the gene in 2006 after taking part in a research study. She described the news as "devastating". Although she was aware of her heightened chances of developing breast cancer given her mother's medical history, the presence of BRCA1 meant that there was little chance she would escape the disease.

The news was shared in a tearful phone call to Elaine. The gene, introduced to the family by the sisters' maternal grandfather, was alive and well in the family bloodline.

The two women decided not to tell their youngest sister at this point as she was pregnant with her second child.

But Karen herself was dealt a harsh reminder of her family history when she discovered a lump in her breast while nursing her newborn.

"I didn't know anything about the gene. To find out about it was a terrible day," Karen said.

For Karen it was too late - the gene had done its work and she underwent a double mastectomy, chemotherapy and radiotherapy within two weeks of diagnosis.

It was devastating for the family to see the youngest suffer, but knowledge of the deadly mutation also gave Elaine and Sue choices. Both sisters decided to have an elective mastectomy and breast reconstruction. Despite the enormity of the decision, they said that it was an easy one to make.

"In the long run it wasn't a hard decision. My other option was to go through my life getting mammograms and ultrasounds. I would always have had hospital in my life," said Elaine.

Sue agreed that losing her natural breasts was a small sacrifice when the threat was so big. "Some people are amazed that you would do this, to lose your breasts. Some people feel as if it is a form of self mutilation, but for me it was a way I could live my life."

The BRCA1 gene also leaves Ashkenazi Jewish woman 50% more likely to develop ovarian cancer. Sue has had her ovaries removed as an added precaution. Both Karen and Elaine plan to do the same, but neither feel ready for it yet.

Despite the difficulties all three women have faced, it is clear that their sisterly love is a great source of strength to them. They may live far apart, but they are in very close contact with each other thanks to modern technology.

Sue yesterday admitted that they found good use of their webcams following their reconstructive surgery. "We would be flashing to each other, showing each other our boob operations," she said.

While all three worry about their own children inheriting the gene, it is clear that life is full of optimism for the sisters.

"I think doing this walk has given me something else to focus on, rather than focus on my health. I think what I learned when mum died so young is that, in life, you have to help people and be positive - travel where you want to travel, and study what you want to. You have one life and I think you have just got to seize it," Karen said.

Dr David Stott, of the University of Glasgow, yesterday thanked the women for their fund-raising efforts. He is researching the immune system's response to breast cancer in a bid to develop a new vaccine. The project is backed and funded by Cancer Research UK.