We were doing Punnett squares in my bio class the other night and one of the problems I was working out was about chances of a person inheriting Huntington's chorea. I thought I had done the problem correctly. Since Huntington's is a dominant disease, I counted any resulting Hh genotypes (one dominant and one recessive allele) as having Huntington's. But then the teacher worked the problem out and said that the genotype would have to be HH (the person MUST have BOTH dominant alleles) in order for the person to have Huntington's chorea. I am completely confused now. I did some Googling and what I am finding seems to support my original assumptions. For instance this: http://evolution.berkeley.edu/evolibrary/article/0_0_0/medicine_05 And I have looked at some other sites which state that an individual inheriting the HH genotype has a very low chance of survival, and will not make it to adulthood. Can anyone help me understand this? Thanks!