Genetic map of the long arm of X chromosome has shown with genetic distances in centimorgans. HPRT, DXS51, FIX, FVIII, St14, DX13 and fragile X site are shown. 

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... B (Christmas disease) is an X- linked recessive bleeding disorder caused by a deficiency or an abnormality of coagulation factor IX. Its birth frequency is about 1 male in every 30000 (1). According to the latest statistical figures, there are approximately 700 hemophilia B affected individuals in Iran (2). A total of eight intragenic RFLP within the factor IX gene have been characterized (3). Hemophilia B carrier detection using both intragenic and extragenic RFLP have been performed (3). A prenatal diagnosis of hemophilia B using intragenic Taq I site has been carried out (4). In families where the mutation has been characterized, direct detection of the gene defect can be applied to carrier and prenatal diagnosis (5, 6). Hemophilia B is less frequent than hemophilia A and is about 1 in 6. Eight-percent factor IX gene mutations are sporadic. The location of the factor IX gene has been narrowed down to the distal portion of band Xq27 (7) ( Fig. 1). The human factor IX gene consists of eight exons and seven introns, spaced out over some 33 kb of chromosomal DNA, which is transcribed to a mRNA of 2803bp (7). Eight intragenic RFLPs which are BamH1, Hhal, Ddel, XmnI, Taq1, MnII, MspI, MseI which are located across a 20 kb region between exons I and VI (3) (Fig. 2). These RFLPs are used for carrier detection and prenatal diangosis (8). The Xmn I have been shown to be in strong linkage disequilibrium with the Taq I polymorphism (8). The frequencies of these intragenic RFLP are high in European populations but low in non- European populations. The second polymorphic sites have been used for carrier detections and prenatal diagnosis, have been performed in Russia (9) using Taq I and Ddel RFLP and also carrier detection are done in Japan using two dinucleotide RFLPs (F9 – 793, F9 – 192) and Hhal RFLP (10). This study presents the results of RFLP analysis for two intragenic polymorphisms in the Iranian hemophilia B families. This is the first investigation of RFLP analysis and carrier detection for hemophilia B in ...

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... the mutation has been characterized, direct detection of the gene defect can be applied to carrier and prenatal diagnosis (5,6). Hemophilia B is less frequent than hemophilia A and is about 1 in 6. Eight-percent factor IX gene mutations are sporadic. The location of the factor IX gene has been narrowed down to the distal portion of band Xq27 (7) (Fig. 1). The human factor IX gene consists of eight exons and seven introns, spaced out over some 33 kb of chromosomal DNA, which is transcribed to a mRNA of 2803bp (7). Eight intragenic RFLPs which are BamH1, Hhal, Ddel, XmnI, Taq1, MnII, MspI, MseI which are located across a 20 kb region between exons I and VI (3) (Fig. 2). These RFLPs are ...