Variation of the non-factor VIII sequences detected by a probe from intron 22 of the factor VIII gene

A severe hemophilia A family has been studied with the factor VIII (F.VIII) intragenic XbaI polymorphism. During this investigation, a new variant hybridization pattern was observed with important implications concerning the non-F.VIII DNA sequences detected by the probe from intron 22, p482.6. Both Southern hybridization studies and direct analysis of amplified DNA demonstrated a variant form of the non-F.VIII sequences. This variant DNA sequence has not been responsible for any detectable phenotypic abnormalities, and likely represents a polymorphic change. In conclusion, this study has shown that the non- F.VIII sequences detected with the probe p482.6 are situated on the X chromosome, they seem to be present in two copies, and either or both copies infrequently possess a polymorphic XbaI site or a partial deletion.