Answer:
See the answer below
Explanation:
First, let us assume that the allele for Huntington's disease is represented by H. An affected person would have HH or Hh gentoype while an unaffected person would be hh.
The genotype of James is either HH or Hh because he is affected for the disease while that of Ava would be hh because she is unaffected.
If James is HH:
HH x hh
Hh Hh Hh Hh
All their offspring would have Hh genotype and hence be affected for the disease. Hence, if James and Ava have a child, the probability that the child will develop Huntington's disease is 100%.
If James is Hh:
Hh x hh
Hh Hh hh hh
Hence, in this case, the probability of the child having the disease is 50%