A diseased man marries a normal woman. They get three daughter and five sons. All the daughter were diseased and sons were normal. The gene of this disease is:

Father gives his X-chromosome to the daughter while Y-chromosome to the sons. In the case, only daughter and none of the sons are affected, the trait is X-linked. Since, daughters get the second copy of $\mathrm{X}$-chromosomes from the mother who is normal and hence does not carry the affected allele of the trait. The trait is expressed in daughters under heterozygous condition, hence it is a X-linked dominant trait