Question

Huntington’s disease is an autosomal dominant inherited disease. People who inherit this disease develop jerky muscle movements, slurred speech, and behavioral and judgment difficulties. A person with Huntington’s disease does not develop symptoms until they are 30 to 50 years of age. Below is a pedigree of a family impacted by Huntington’s Disease.



Individual 12 wants to have children and his partner does not have Huntington’s disease. Based on the reading and pedigree, to what extent should individual 12 be concerned about passing this genetic disease to his offspring?

Because individuals 13 and 14 are affected siblings, individual 12 likely inherited the dominant allele and has a high chance of passing it to his offspring.

Individual 12 is a possible carrier and should be concerned about passing this trait to his children

Since individual 12 is homozygous recessive, he would not have to worry about passing the genetic disorder to his children.

His future children will most likely be impacted because his parents, individuals 7 and 8, have Huntington’s Disease.

Answer 1

Best choice: "Individual 12 is a possible carrier and should be concerned about passing this trait to his children."

Why: Huntington disease is autosomal dominant. If a parent carries the mutated allele, each child has a 50% chance of inheriting it. The fact that siblings 13 and 14 are affected means at least one parent is (or was) a mutation carrier, so individual 12 has about a 50% chance of having inherited the mutation even if he is not yet symptomatic (Huntington’s usually has onset at 30–50 years). If he does carry the mutation, each of his children would have a 50% chance of inheriting it.

Recommended next steps: genetic counseling and predictive genetic testing before making reproductive decisions; if he is positive, options include preimplantation genetic diagnosis (PGD), prenatal testing, or alternative family-building options.