GENETIC MECHANISM OF CIS-AB INHERITANCE .1. A CASE ASSOCIATED WITH UNEQUAL CHROMOSOMAL CROSSING OVER

  • 1 January 1980
    • journal article
    • research article
    • Vol. 32  (3) , 332-338
Abstract
In contradiction to the general Mendelian inheritance of blood group ABO expression, the A and B characteristics are inherited together from 1 parent in the rare cis-AB phenotype. Since the synthesis of blood group A and B substances are controlled by N-acetylgalactosaminyltransferase (A-enzyme) and galactosyltransferase (B-enzyme), the genetic mechanism of cis-AB expression may be elicidated by examining the characteristics of A- and B-enzymes in cis-AB plasma. Biochemical study reveals that the examined cis-AB plasma contains 2 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. 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.