Huntington's disease is caused by the allele h, which is completely dominant to the normal recessive allele h. consider a couple where the man has the genotype hh, and the woman has the genotype hh. what is the chance that their child will develop huntington's disease?

Thr genotypes of the parents are Hh heterozygote (the father) and hh recessive homozygote (the mother).
The father has a dominant allele (H) that causes him to develop Huntington disease.
As you can see in the punnet square presented below, he will pass this H allele to a half of his offspring, giving them Huntington's disease too.
So, the possibility of the offspring of this couple having Huntington's disease is 50%.