Examples of X-inactivation analysis. Amplification by polymerase chain reaction across the HUMARA polymorphism was performed as described in the Materials and Methods. Lanes marked f show the allele amplified from the father of the female studied in the next two lanes; − is without Hpa II digestion and + is with Hpa II digestion before amplification. Lanes 2, 3, and 5 through 12 show females from X-linked families. In these samples note the skewed inactivation patterns, although lane 12 is incompletely skewed. Lanes 13 and 14 show a normal pattern in the mother of family 024.