Question

ntington’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?

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

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

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.

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

Answer 1

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

Why:
- Huntington disease is autosomal dominant and often has late onset (30–50 yrs). A person can carry the disease-causing allele and be asymptomatic at childbearing age, yet still pass the allele to offspring.
- If individual 12 does carry the mutant allele, each child would have a 50% chance of inheriting it (partner is unaffected).
- The word “carrier” is usually used for recessive conditions; for dominant diseases it’s clearer to say he may carry the disease-causing mutation or be presymptomatic.

Why the other choices are incorrect:
- “His future children will most likely be impacted because his parents…have Huntington’s Disease.” — Not necessarily; the actual risk to his children depends on whether individual 12 inherited the mutation. You can’t assume the children will “most likely” be affected without his genotype.
- “Because individuals 13 and 14 are affected siblings, individual 12 likely inherited the dominant allele…” — Two affected siblings increase family risk but do not prove individual 12 inherited the allele. Each sibling’s inheritance is independent (assuming heterozygous parents, each child’s risk is ~50%).
- “Since individual 12 is homozygous recessive…” — There is no evidence he is homozygous recessive, and that phrasing misunderstands autosomal dominant inheritance.

Next steps:
- Recommend genetic counseling and offered predictive genetic testing so individual 12 can know his status and make informed reproductive decisions (including prenatal testing or IVF with PGD if desired).