RT-PCR analysis of the F. IX transcripts. Total RNA was isolated from the livers of 4-week-old carrier female, affected male, normal litter mate, and normal adult male mice. PCR amplifications were performed for 30 cycles under the following conditions: 94°C for 1 minute, 55°C for 45 seconds, and 72°C for 45 seconds using an F. IX exon f sense primer and an exon h antisense primer. The length of the PCR product corresponding to the exon f and exon h portion of the F. IX transcripts is 713-bp (lanes 1 to 7). 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, normal 6-month-old adult (A) male, lane 6, no. 93, carrier (C) female; lane 8, 100-bp ladder; mouse 18S ribosomal primers were used as loading control. The PCR fragment obtained by amplification of the 18S rRNA transcript for all samples is 488 bp and was shown below the corresponding lanes.