(A) Northern analysis of the F. IX transcripts. Total liver RNA (25 μg) samples from 4-week-old carrier female, hemizygous male, normal litter mate, and normal adult male mice were loaded into 0.8% agarose-formaldehyde gel and transferred to a nylon membrane. The membrane was hybridized with a 0.644-kb factor IX cDNA as described in Materials and Methods. The normal sizes of the F. IX transcripts are 3.2 kb and 2.2 kb. Lanes 1 and 7, nos. 90 and 95, normal (N) males; lane 2, no. 92, normal (N) female; lanes 3 and 4, nos. 89 and 91, hemophilic (H) males; lane 5, control 6-month-old adult (A) male; lane 6, no. 93, carrier (C) female; below, hybridization of the filter with a GAPDH probe as internal standard. (B) Plasma F. IX coagulant titer, expressed as U/dL, of carrier females, hemizygous male, and normal mice are shown in corresponding lanes.