Dominant inheritance occurs when an mutant gene from ONE parent is capable of causing disease, even though a matching gene from the other parent is normal. The abnormal gene dominates the gene pair. Males inherit 1 X chromosome from their mother, and 1 Y chromosome from their father, which carries little information other than maleness. Females have 2 X chromosomes, 1 each from their mother and father. In an X-linked dominant disorder: If the father carries the abnormal X gene and the mother doesn’t, the entire female offspring will inherit the disease and none of the male offspring will have the disease. If the mother carries one abnormal X gene, 50% of the entire offspring (females and males) will inherit the disease tendency.
Affected sire X clear dam = 100% clear males + 100% affected (heterozygous) females
Clear Sire X Heterozygous (Affected) Dam = 50% Affected (males and females) + 50 % clear (males and females)
Clear sire X Homozygous (Affected) Dam = 100% Affected Offspring.