It's Saturday afternoon and 6-year-old Kailyn Whaley is scooting her toy car around the living room of her family's Alpine home while her 4-year-old sister, Charis, stacks building blocks a few feet away. Playing is something they can do on their own.
But there's a lot they can't do. They can't string together more than a few words. They can't walk. They can't do most routine tasks without help.
"I would've never thought that I'd have two children with any kind of disease," said their mother, Christina Whaley. "Unfortunately, that was what happened."
It happened because Whaley passed down faulty mitochondria to both of them.
Mitochondria power all the cells in your body, and you get them directly from your mother. The DNA in Whaley's mitochondria is mutated.
"Every egg that I have is going to have some percentage of the mutation," she explained.
Whaley's daughters both have a rare type of mitochondrial disease known as NARP, short for neuropathy, ataxia, and retinitis pigmentosa. Lifespan varies for NARP patients, but kids with severe forms of mitochondrial disease often don't live past childhood.
Whaley comes from a big family. Her mother never had mitochondrial disease, nor did any of her five siblings. Her mitochondria is not mutated enough to have made an impact on her health so far — doctors have even told her that if she never had kids, she probably would never have known she had mitochondrial disease at all.
After Whaley noticed Kailyn wasn't walking on time, she started going to doctors to find out why. It took her more than two years to pin down a diagnosis. By then, Whaley had already given birth to Charis, not realizing she was passing down the same disease.
"My dream was to have three to four kids," said Whaley. "That was always the idea and the plan. What ages I was going to have them and how spaced apart and what month I was going to get pregnant in. Everything was all figured out."
Doctors have advised Whaley against having any more children.
But soon, they might be able to offer another option. Scientists have been developing a twist on in vitro fertilization that could help mothers like Whaley have children of their own without passing on disease. This month, lawmakers in the United Kingdom voted in favor of the procedure. But things are moving more slowly in the United States as scientists debate the safety and ethics of trying the experimental technique in humans.
It's still a long ways from any fertility clinic, but here's how it could work:
Doctors would extract an egg from the mother carrying bad mitochondria. They would remove the nucleus from that egg, and with it, the genetic traits mom would pass down to her kids. Then, they would implant that nucleus inside another egg donated by a different woman, an egg with healthy mitochondria. Fertilize that egg with dad's sperm, and in theory, you would end up with a baby free of mitochondrial disease.
But, because mitochondria do contain their own DNA, any child produced this way would inherit a small fraction—far less than one percent—of their DNA from that second woman. That's why some have called this technique three-parent in vitro fertilization.
"This term is meant to be inflammatory and pejorative," said Evan Synder, professor at the Sanford-Burnham Medical Research Institute in La Jolla.
Snyder prefers the term nuclear transfer. But whatever you call the procedure, it's highly controversial, something Synder knows well. Last year he chaired the FDA committee tasked with considering whether or not this procedure should be tried in humans.
Members of his committee were generally in favor, but they wanted to see more animal studies before moving forward.
Even that cautious conclusion spurred debate. Skeptics think manipulating embryos to this extent could put medicine on the slippery slope toward designer babies.
"That typically is what comes up," Synder said. "If we do it for mitochondrial diseases, will we start doing it for sex? Or for prowess in academics or sports?"
Snyder said this specific procedure wouldn't let parents anywhere near genes for traits like eye color. That's why he felt comfortable advocating a yes vote in the U.K.
"I absolutely feel that the U.K. made the right decision," he said.
Paul Knoepfler, a UC Davis School of Medicine professor, disagrees, saying, "I really felt this vote was premature."
He said this technique would create genetically modified humans, and he worries that using it in an attempt to stamp out mitochondrial disease could lead to equally bad developmental disorders, or miscarriage. He also points out that any unexpected problems in children born this way could become hereditary.
"We're talking about permanently changing human DNA," Knoepfler said. "And so I think it is reasonable to think about how this could have repercussions for many generations in the future."
Meanwhile, mothers like Christina Whaley are hopeful about any new options.
"I definitely can't imagine my life without having children in it," she said. "And of course I want a healthy child."
She has heard the concerns. And she realizes the procedure may not be affordable or approved any time soon. But if the option were available tomorrow, she says she would try it right away.
