Watching their beloved mother Susan slowly die from Motor Neurone Disease was devastating for Jessica and Kaitlin Ellis.
Having to tell her they would both almost certainly die from the same disease almost broke their hearts.
After their mother's diagnosis in 2015, the sisters made a pact to undergo genetic testing together to see if they too carried one of the main genes related to MND.
Three months later they received the terrible news that they had the C9ORF72 gene - and were told that meant they had a 99 per cent chance of getting MND.
"It's a personal choice whether you get tested - for me it helps to know so that at least I can be prepared for it," Jessica, 28, said. "I think it would be harder if I didn't know.
"The hardest part was telling our mum - I still remember her wail of despair. It must have been bad for her to know her only children had the same fate as her.
"The only thing we could do was assure her we'd make the most of our lives - and that now we knew, we could stop the gene with us."
Jessica and sister Kaitlin, 25, are from south-west Sydney, but visited the Illawarra Health and Medical Research Institute on Wednesday to learn more about the ongoing research into MND under renowned scientist Professor Justin Yerbury.
"Only 10 per cent of MND is familial," Kaitlin said.
"My mum's brother was diagnosed in 2010 and died 18 months later. So when my mum was diagnosed in February 2015, my sister and I decided to take the test.
"Dealing with her new diagnosis, and the knowledge that it would one day be us, was hard. But we just concentrated on giving the best life to my mum."
The sisters cared for their mum, as she progressively lost the ability to walk, talk, eat and swallow. "We pretty much watched her starve to death - it was horrendous," Kaitlin said.
After she died in 2017, their thoughts turned back to their own plight. "Every little twitch, every time I couldn't open something - I'd think 'it's happening to me now'," Kaitlin said.
Rather than dwell on it they decided to reach out to others and formed support group MND Genies along with friend Rebecca Young, who carries the SOD1 gene also related to MND.
The positive test means they have to plan carefully for their future, including looking at IVF if they want to start a family.
"I lost my dad in 2007 to MND when I was just 14, and then my aunty died of the same disease," Rebecca said.
"I got tested about three years ago and am now planning my future with my fiancee Adrian, and we will go through IVF to make sure we don't pass on the gene.
"You have to plan every aspect of your life carefully, as you feel like you're living on borrowed time, and you want to make the most of the time you have."
Rebecca said meeting the Ellis sisters had meant she no longer felt alone with her. "We have a connection I can't describe," she said. "We know what each other is going through."
The young women are encouraged by ongoing research, which in the sisters' case has led to their risk of developing MND being lowered to 50 per cent.
And they draw inspiration from Prof Yerbury, who lost his mother and other relatives to MND before undergoing the test and then being diagnosed with the disease.
Prof Yerbury said: "I guess that I wasn't surprised by the results of the test, but I also knew that my grandmother had lived a full life before being diagnosed at 72 so there was always hope even after such bad news. I really just took things one day at a time.
"The decision to have a genetic test is a very personal one. But I would tell someone with MND or with a genetic mutation the same thing I would tell anybody else.
"Make the most of every day on this earth, live for every moment because you never know what is around the corner."
Currently Prof Yerbury and his team at IHMRI, based at the University of Wollongong, are investigating why motor neurons die during MND. They can then use that information to design therapies that can be tested in the laboratory.
There is no cure, nor definitive treatment, for MND but Prof Yerbury is confident that will change.
"We have recently seen the first successful treatment for any MND. That is the childhood disease SMA," he said.
"This is very exciting news and it won't be long until gene therapies for some forms of familial MND are finished clinical trials and are on the market."