Hemophilia is a rare disorder in which your blood doesn't clot normally because it lacks sufficient blood-clotting proteins (clotting factors). Hemophilia is a sex-linked recessive disorder. The gene with the instructions for making factor is found only on the sex chromosome labeled X. This genogram shows the family pedigree when the mother is a carrier and the father is normal. A pedigree is a chart that displays family information in an easy-to-understand style. It's commonly referred to as a "family tree." A standardized set of symbols is used in pedigrees, with squares representing men and circles representing females. The building of a pedigree is a family history, and details about a previous generation may be hazy as memories fade. A diamond is used if the person's sex is uncertain. A filled-in (darker) symbol represents someone who has the trait in question. Heterozygotes are denoted by a shade dot inside a symbol or a half-filled symbol when they are identifiable.