1 Pedigree with X-linked recessive disorder. A - is Lesch-Nyhan syndrome family drawn based on the data of Nyhan, B - is hemophilia in a family described by Coleman Rand coworkers. Female IV -1 in A and 11-1 in B are very rare instances where a female expresses an X-linked recessive disorder in spite of carrying a dominant normal allele. In A, IV-1 has inherited the disease from a normal mother, in B 11-1 inherits the disease from an affected hemizygous father.