There are time-bombs ticking in the DNA of couples across the country, and Rachael and Jonathan Casella have made it their mission to defuse them.

In 2017, the Casellas lost their beautiful baby girl Mackenzie when she was just seven months old.

Today, a $20 million genetic study of 10,000 couples, named ‘Mackenzie’s Mission’ in her honour, is being rolled out across the country.

“It’s bittersweet,” Rachael Casella told Deborah Knight.

“We’re like any parent – we love to talk about our child, we’re proud and we love her desperately, but we don’t get to have her in our arms.

“Talking about her is the best thing that we can do to keep her around.”

Mrs Casella says one of the most frightening aspects of genetic diseases is how difficult they are to identify.

She had a “perfect” pregnancy, she said, and didn’t even notice any symptoms until Mackenzie was ten weeks old.

Mackenzie was diagnosed with spinal muscular atrophy (SMA): a rare disorder, but nevertheless the leading genetic cause of death in children under two.

“One in 20 babies is born with a genetic condition or a birth defect,” Mrs Casella said.

“So when we start looking at those numbers, we can’t help but ask ‘why’.

“I hate to break it to everyone, but every single person who’s listening to this has on average three to five genetic conditions in their DNA.

“What happened to us, we’re not unique, we’re not special in any way.”

The government-funded Mackenzie’s Mission study will screen volunteer couples for 1,300 severe, life-limiting or lethal conditions.

“There are also some of them that actually have treatments if you get early intervention, so we’re trying to save lives as well.”

Rachael and Jonathan say despite the difficult days, they ‘owed it’ to Mackenzie to persevere.

“Ultimately our story is of love: grief is love.

“She’s a gift.”

Click PLAY below to hear the full interview