Huntington disease is an autosomal dominant disorder that leads to progressive degeneration of brain cells. there is no effective treatment for the disorder and individuals usually die in their 40s or 50s, 10 to 15 years after the onset of symptoms. which of these statements about huntington disease is true?

-huntington disease can only be inherited when a parent is showing the trait.
-huntington disease usually appears during middle age.
-as an autosomal dominant disease, huntington disease is expressed only if both parents carry the trait.
-huntington disease usually skips a generation.