Heteroduplex screening for molecular defects in factor IX genes from haemophilia B families

Heteroduplex screening of amplified fragments containing sequences of all known small haemophilic mutations in the factor IX gene localized mutations in 18 new families: 12 were at common recurrent sites; three were novel. Carriers and/or patients from each of 41 families with mutations in 7 exons and 5' and 3' non-coding regions were positive.