crossing over between the two repeated domains, is responsible for the formation of the Ge-2,-3 genotype. The breakpoints of the deletion are located within introns 2 and 3 and results in the deletion of exon 3. This mutant gene is transcribed as a messenger RNA with a continuous open reading frame extending over 300 nucleotides and is translated into the sialoglycoprotein found on Ge-2,-3 red cells. A second 3.4 kilobase pair deletion within the glycophorin C gene eliminates only exon 2 by a similar mechanism and generates the mutant gene encoding for the abnormal glycoprotein found on Ge-2,+3 erythrocytes. The Ge2 epitope is antigenic only on glycophorin D and is a cryptic antigen in glycophorin C. It is located within exon 2 and is sensitive to trypsin and papain but resistant to chymotrypsin and pronase. The Ge3 epitope is encoded by exon 3. It is sensitive to trypsin but resistant to chymotrypsin, papain and pronase. It is thought to lie in the between amino acids 42-50 in glycophorin C (residues 21-49 in glycophorin D). Ge4 is located within the first 21 amino acids of glycophorin C. It is sensitive to trypsin, papain, pronase and neuraminidase. Leach antigen The relatively rare Leach phenotype is due either to a deletion in exons 3 and 4 or to a frameshift mutation causing a premature stop codon in the glycophorin C gene, and persons with this phenotype are less susceptible (~60% of the control rate) to invasion by Plasmodium falciparum. Such individuals have a subtype of a condition called hereditary elliptocytosis. The abnormally shaped cells are known as elliptocytes or cameloid cells. The basis for this phenotype was first reported by Telen et al. The phenotype is Ge:-2,-3,-4. Yussef antigen The Yussef (Yus) phenotype is due to a 57 base pair deletion corresponding to exon 2. The antigen is known as GPC Yus. Glycophorin C mutations are rare in most of the Western world, but are more common in some places where malaria is endemic. In Melanesia a greater percentage of the population is Gerbich negative (46.5%) than in any other part of the world. The incidence of Gerbich-negative phenotype caused by an exon 3 deletion in the Wosera (East Sepik Province) and Liksul (Madang Province) populations of Papua New Guinea is 0.463 and 0.176 respectively. Webb antigen The rare Webb (Wb) antigen (~1/1000 donors), originally described in 1963 in Australia, is the result