A woman with severe discoloration of her tooth enamel has four children with a man who has normal tooth enamel. Two of the children, a boy (B) and a girl (G) have discolored enamel. Each has a mate with normal tooth enamel and produces several children. G has six children, four boys and two girls. Two of her boys and one of her girls have discolored enamel. B has seven children, four girls and three boys. All four of his daughters have discolored enamel, but all his boys have normal enamel Decide on the inheritance mode of this condition, and explain why.