Danny and his mother had already done their crying when they told other family members. He was getting ready to go to the Missionary Training Center. And he decided he just couldn't do it. Then he changed his mind.

"It seemed to me that a mission was a very good place for me to be for the next two years.

"This disease has really opened my eyes," he says today. "I remember my dad starting to get sick. I was 10 or 11, and financially it went downhill fast. I thought that happened to everybody. I would see some of my friends and think, 'Man, that's going to suck when it happens to them.' "

That it doesn't happen to everyone is driven home to him a lot. He played gene roulette unwillingly and seems to have lost. But he's determined not to let it ruin his life, as it has so many others who forget to live in the present while they're busy dreading the future.

"HD will and won't affect my future," he says. "I had to decide, if I have Huntington's, do I want to get married. I know that I need to be married and have a family. Because I have this doesn't necessarily mean I won't do those things. But I will do them differently."

He has a gift that John, Amy and Julie were denied, he says. Time to plan. And to save. "My dad's disease hurt my mom financially. I can do some planning for it. So it will affect me, but some of it will be in a good way."

He knows that the only way to eradicate Huntington's at this point is to choose not to have biological children. And he will grapple with that. In the meantime, he watches with interest scientific advances.

It is possible now to do gene testing on a fertilized egg to see if it contains the mutation, according to Dr. Jay Jacobson, a bioethicist at the University and LDS hospitals. Eggs could be fertilized and tested, and one that was mutation-free could be implanted using in vitro fertilization. The technology exists, although no one seems sure if it has been used with Huntington's disease yet. It's very possible that sperm could be tested prior to fertilization, researchers say.