"But you wouldn't have the later years -- you'd remain physically and functionally able," he said.
That is why he believes his study of Gabby Williams' genetic code is so important. "She fits the model," said Walker.
"We've been on this journey to find out, are my other children at any risk in having a child like Gabrielle," said Williams, who has five other children between the ages of 1 and 10.
"We did find out with Dr. Walker when he did the [gene] sequencing that it's not something we can pass on but just an abnormality, a mutated gene that was just happenstance," she said. "That was a relief for us."
At first, when the Williams family members found out about Walker's research, they hesitated to become guinea pigs in the studies that would promote a so-called "fountain of youth."
"There was some concern," she said. "We are good Catholics, God-fearing people and we believe we are meant to get old -- the process of life -- and meant to die. It was scary to think about, and we did not want to be part of it."
But as they talked further with Walker, the family realized that his research was designed to help people struggling with the impairments of old age.
"Alzheimer's is one of the scariest diseases out there," said Williams. "If what Gabrielle holds inside of her would find a cure -- for sure we would be a part of the research project. We have faith that Dr. Walker and the scientific community do find something focused more on the disease of aging, rather than making you 35 for the rest of your life."
As for Gabby's life span, her doctors cannot say what that will look like.
"From the time of her birth, we didn't think she would be with us very long," said her mother. "The fact is she is now going on 9 years. She kind of surpassed my expectations from the get go.
"It's not something I worry about," said Williams, who said she trusts that God has a plan for her infantile daughter.
"When he is ready to take her back, it will be sad," she said. "But what a glorious thing it will be for Gabby to go to heaven one day. I know it will happen, but I am not hoping it's any day soon."