Densitometry plots of X-inactivation analysis. Individual lanes showing amplification of the HUMARA gene after Hpa II digestion are plotted using the NIH image program. Autoradiographs were exposed for less than 16 hours. (A) The incompletely skewed female shown in lane 12 of Fig 2 (family 6, II:4). (B) The other incompletely skewed female from an X-linked family (family 005, III:3). (C) The mother of an affected boy from the family with an uncertain pattern of inheritance (family 009, II:12). (D) Her sister (family 009, II:1).