Assume That a Human Gene Is Imprinted

Short Answer

Assume that a human gene is imprinted. Normal individuals have one active copy of the gene, the copy inherited from their fathers. The copy inherited from their mothers is normally inactive.
In one large family a mutation in this gene occurs and this mutation results in part of the gene being deleted. The defective gene is never active regardless of the parent from which it is inherited. Individuals who carry the mutation are heterozygous and also have a normal copy of the gene whose activity depends upon which parent it was inherited from. Individuals who have no active copy of the gene have several medical problems but live long enough to have children of their own. This family includes two phenotypically normal parents who have two affected children, a son and a daughter. Which parent, father or mother, did the affected children inherit this mutation from? Why?