All five of the children in a family were born with a genetic disorder. The disorder is inherited as autosomal dominant. If this is not a statistical rarity, the likelihood would be that:

Question

1. One parent has both chromosomes with the affected gene.
2. Both parents are carriers.
3. One parent is a carrier and the other parent is unaffected.
4. One parent has one chromosome affected and the other parent has none.

Answer 1

1
Rationale 1: It takes only one chromosome to cause the defect in the child. If one parent has both chromosomes affected, every child would receive the affected chromosome.
Rationale 2: If both parents are carriers, 25% of the children should be free of the disease.
Rationale 3: For all five children to have the disorder, one parent would have to have both chromosomes affected.
Rationale 4: For all five children to have the disorder, one parent would have to have both chromosomes affected.
Global Rationale: