Class 12 NEET Biology Principles of Inheritance and Variation Questions Part 1

In the inheritance pattern of sex chromosomes X-chromosome of father always passes to daughter and X -chromosome of mother passes to son. As the father is diseased and all the girls inherit it, it is obvious the disease is sex-linked. The mother is not a carrier (as evident from the fact that no son is diseased). Thus, the gene is dominant and expresses even in heterozygous condition.