A woman comes to your genetic counseling center because she knows that Huntington disease occurs in members of her family. Her paternal grandfather was afflicted, but so far her father shows no symptoms. Her two great-great grandmothers on her father's side were healthy well into their 90s, and one of her great-great grandfathers died of unknown causes at 45. Testing for Huntington disease is extremely expensive, but she is concerned that she may fall victim to this disease and wants to plan her life accordingly. After examining her pedigree you advise her to  A. not get tested because there is no possibility that she is homozygous. B. not get tested because only males in her family get the disease. C. get tested because her father could be a carrier. D. not get tested because her father is only a carrier and it is very unlikely her mother is a carrier. E. not get tested because her 40-year-old father shows no symptoms.

As Huntington Disease is an inherited dominant disease, it means that is enough the presence of one allele to develop illness. Her paternal grandfather was affected but not her father great-great grandmothers. Is her father, carrier of an HD allele? The problem here is that we can’t be sure her father is not a carrier, because although he’s 40 years old and doesn’t show symptoms of illness, HD uses to appear between 30 to 50 year old ages, but it can appear at any age. Eventually a possibility for the disease to appear, is still possible.