Haemopoietic chimaerism: a complication in heterozygote detection tests for inherited defects in cattle.

Summary Several observations are documented which illustrate that haemopoietic chimaerism is a potential source of error when using assays of cellular components of blood to determine genotype for inherited defects in cattle. Acidic α-glucosidase activity in peripheral mononuclear cells of a twin Brahman bull that had sired calves affected with generalized glycogenosis was similar to that in cells from homozygous normal animals. Activity in fibroblasts from this bull was similar to that in heterozygotes. α-mannosidase activity in fibroblasts of a twin Murray Grey bull with low activity in peripheral granulocytes but high activity in plasma was similar to that in animals homozygous normal for α-mannosidosis. Normal argininosuccinate synthetase nucleotide sequence was detected in leucocytes from two calves affected with citrullinaemia and mutant sequence detected in leucocytes from their homozygous normal co-twins.