Faculty Articles


SfaNI Polymorphism Distinguishes the Alleles of the Glycophorin A Locus that Determine the MN Blood Group



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Acta haematologica





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The GPA gene is a single-copy autosomal gene coding for the major erythroid cell-specific sialoglycoprotein, glycophorin A. Two common GPA alleles are present in the human population, coding for proteins that differ at the first and fifth amino acids of the mature protein. These two alleleic forms of GPA are expressed codominately in heterozyogous GPAM/N individuals and serve to determin the MN blood group. The nucleotide sequences of the cloned GPAM and GPAN cDNAs have been determined and the protein polymorphisms are attributable to three nucleotide substitutions, one in the middle of codon 1 and two clustered at the end of codon 5. Computer analysis of these sequences revealed five restriction enzymes capable of unambiguously distinguishing these alleles, four of which are frequently cutting enzymes with 4-bp recognition sequences, as well as a unique SfaNI site in the first codon of the M allele which is disrupted by the single base change in the corresponding region of the N allele. This SfaNI polymorphism differs from most such RFLPs in that it was predicted by sequence analysis rather than found by screening with a random battery of restriction enzymes. Moreover, this SfaNI RFLP is intrinsically linked with the basis of the MN blood group phenotype. This polymorphism should be useful in forensic studies to match blood typing data with solid tissue samples. The system also lends itself well to polymerase chain reaction adaptation, with restriction enzyme recognition sites for each of the single base pair differences distinguishing the M and N alleles in codon 1, as well as restriction sites specific for each of the 2-bp differences observed in codon 5.


Medical Specialties | Medicine and Health Sciences | Osteopathic Medicine and Osteopathy

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