Question

Annette's maternal grandfather died of Huntington's disease when he was 53 and Annette was 8. Huntington's is a rare autosomal dominant degenerative neural disorder that usually hits people in their late forties, early fifties. Annette loved her grandfather very much and was deeply affected by the painful progression of his disease. She wants to get pregnant but does not want to risk giving birth to a child that will suffer as much as her grandfather. If she tested positive for Huntington's, what is the probability of her first child to develop Huntington's? Of her second child? Of her mother? (Note that since Huntington’s is so rare, you can assume that neither grandmother, nor father or partner have the Huntington’s mutation).