The molecular genetics of blood group polymorphism |
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Authors: | Geoff Daniels |
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Institution: | (1) Bristol Institute for Transfusion Sciences, NHS Blood and Transplant, North Bristol Park, Filton, Bristol, BS34 7QH, UK |
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Abstract: | Over 300 blood group specificities on red cells have been identified, many of which are polymorphic. The molecular mechanisms
responsible for these polymorphisms are diverse, though many simply represent single nucleotide polymorphisms (SNPs). Other
mechanisms include the following: gene deletion; single nucleotide deletion and sequence duplication, which introduce reading-frame
shifts; nonsense mutation; intergenic recombination between closely linked genes, giving rise to hybrid genes and hybrid proteins;
and a SNP in the promoter region of a blood group gene. Examples of these various genetic mechanisms are taken from the ABO,
Rh, Kell, and Duffy blood group systems. Null phenotypes, in which no antigens of a blood group system are expressed, are
not generally polymorphic, but provide good examples of the effect of inactivating mutations on blood group expression. As
natural human ‘knock-outs’, null phenotypes provide useful clues to the functions of blood group antigens. Knowledge of the
molecular backgrounds of blood group polymorphisms provides a means to predict blood group phenotypes from genomic DNA. This
has two main applications in transfusion medicine: determination of foetal blood groups to assess whether the foetus is at
risk from haemolytic disease and ascertainment of blood group phenotypes in multiply transfused, transfusion-dependent patients,
where serological tests are precluded by the presence of donor red cells. Other applications are being developed for the future. |
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