Question

If Huntington's disease is due to a dominant trait, shouldn't three-fourths of the population have Huntington's while one-forth has the normal phenotype?

Answer 1

Not necessarily, no. First of all, when humans breed, there are different genotypic offspring. Huttington's is dominant, but if you have 2 parents who dont have it and they cross, then of course their offspring wont have it. Not everyone is a carrier so no, 3/4 population would not have it