Correcting some misinformation in the previous post:

Huntington's disease is genetic, but is NOT sex-linked. It is caused by a single dominant gene. If either parent has it, all children have a 50/50 chance of inheriting it. If a child escapes the disease, he will not pass it on to his or her offspring. Until recent advances in genetic testing, the only way to know if you had it was to wait for the onset of symptoms in mid-life, after the age when you'd started the next generation of the family. With genetic tests, it can now be diagnosed before one starts a family, but there is still no cure.

More information at the National Institute of Neurological Disorders and Stroke website.

--Charlie Baum