Genetic diagnosis of two haemophilia families with recombination / 中华检验医学杂志

ABSTRACT

objective To make genetic diagnosis in two haemophilia families with recombination. Methods For hemophilia A(HA)family,screening of the F Ⅷ intron 22 and intron 1 inversion mutations was employed to identify the mutation. Linkage analysis with 8 polymorphic markers was adopted in the pedigree. For hemophilia B(HB)family,DNA sequencing of all coding regions of FⅨ gene Was used to detect the mutation directly. The muhifluorescent PCR method employing six FⅨ related STR was adopted in linkage analysis.Results In the HA family,the proband was positive in inversion 1 detection and the relative female was inversion 1 carrier. But linkage analysis with polymorphic markers showed contrary resuhs. Some markers certified that the female inherited the disease chromosome of the family while the others showed contrary results.In the HB family,it was unsuccessful in sequencing the exon 7 of the F Ⅸ gene in the proband and there was no mutation found in the other parts. The relative female and her amniocyte DNA were successful in sequencing the whole F Ⅸ gene and no mutation was detected.The linkage analysis of the family showed contrary results. Recombination occured in these two families. Conclusions Although the linkage analysis iS convenient and effective in carrier and prenatal diagnosis of hemophilia families. The recombination risk shouldn't be neglected especially when the polymorphic markers give inconsistent information for linkage analysis. It is necessary to find some high inforrnative markers intragenic or on the telomeric side to the gene in order to prevent the risk of recombination.