ABO Rhesus blood hemolytic Hirschsprung adu group disease disease stature Mendelian polygenIc (monogenic Figure 3.1 Human Molecular Genetics, 4ed (o Garland Science) ABO blood group depends (with rare exceptions) on the genotype at just one locus, the AB0 locus at chromosome 9q34 rhesus hemolytic disease of the newborn depends on the genotypes of mother and baby at the RHD locus at chromosome 1p36, but also on mother and baby's being aBo compatible. Hirschsprung disease depends on the interaction of several genetic loci. Adult stature is determined by the cumulative small effects of many loci. Environmental factors are also important in the etiology of rhesus hemolytic disease, Hirschsprung disease, and adult height.• ABO blood group depends (with rare exceptions) on the genotype at just one locus, the ABO locus at chromosome 9q34. Rhesus hemolytic disease of the newborn depends on the genotypes of mother and baby at the RHD locus at chromosome 1p36, but also on mother and baby's being ABO compatible. Hirschsprung disease depends on the interaction of several genetic loci. Adult stature is determined by the cumulative small effects of many loci. Environmental factors are also important in the etiology of Rhesus hemolytic disease, Hirschsprung disease, and adult height