Genetic mechanism of cis-AB inheritance. I. A case associated with unequal chromosomal crossing over.
In contradiction to the general Mendelian inheritance of blood group ABO expression, the A and B characteristics are inherited together from one parent in the rare Cis-AB phenotype. Since the synthesis of blood group A and B substances are controlled by N-acetylgalactosoaminyltransferase (A-enzyme) and galactosyltransferase (B-enzyme), the genetic mechanism of Cis-AB expression may be elucidated by examining the characteristics of A- and B-enzymes in Cis-AB plasma. Biochemical study reveals that the examined Cis-AB plasma contains two separable enzyme components: one with kinetic properties similar to those of common A2-enzyme, but differing from A1-enzyme, and another with kinetic characteristics similar to those of common B-enzyme. Therefore, Cis-AB expression, at least in the case examined, is due to unequal crossing over, producing a chromosome with alleles for A2- and B-enzymes, rather than to a structural mutation in A or B alleles producing a single abnormal enzyme with bifunctional activity.
D000017:ABO Blood-Group System / Q000235:genetics*; D000328:Adult; D002847:Chromatography, Agarose; D003434:Crossing Over, Genetic; D005643:Fucose / Q000031:analogs & derivatives / Q000235:genetics; D005688:Galactosamine / Q000235:genetics; D005700:Galactosyltransferases / Q000097:blood / Q000235:genetics*; D008040:Genetic Linkage; D006386:Hemagglutination Tests; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D008957:Models, Genetic; D017350:N-Acetylgalactosaminyltransferases; D010375:Pedigree
D000017:ABO Blood-Group System; D005643:Fucose; D005688:Galactosamine; D005700:Galactosyltransferases; D017350:N-Acetylgalactosaminyltransferases; C003742:UDPgalactosamine-galactose acetylgalactosaminyltransferase; C023155:blood-group-substance alpha-D-galactosyltransferase