It is a literal 50% chance of developing the disease. Let's say H represents the allele for Huntington's.. and h represents normal. Then the father would be Hh, and the mother would be hh. Then in having a child, there is a 50% chance of the child being Hh, 50% chance of the child being hh. (we...
I know that if one parent has HD then there is a 50% chance that their child will inherit the disease. Because let's say H represents the dominant allele (bad) for HD.. and h represents the recessive (normal).. If one parent (Hh) carries the disease, and the other (hh) doesn't have the disease...