Huntington’s disease
...n displaying symptoms between the ages of 30 and 50, but has been known to show itself in people as young as two and as old as 80. Huntington's disease is inherited from one of the victim's parents. Since the gene for HD is dominant, there is a 50% chance of a sufferer's offspring inheriting the disease. Because a victim usually does not begin to display symptoms until after the period in which he or she would have children and the disease may have been misdiagnosed in earlier generations as Parkinson's disease or other similar affliction, he or she might pass along the gene without even knowing it. The gene for Huntington's disease is located on chromosome four. It was first identified in 1993. While everyone possesses this gene, in someone suffering from Huntington's disease, the number of repeats of a certain trinucleotide, cytosine-adenine- guanine (CAG), is much larger than what it is in a normal person. In an average person, the number of repeats is between 9 and 37. But the person with HD the repeat count...