THE ASSAY OF GALACTOKINASE AND GALACTOSE-1-PHOSPHATE URIDYL TRANSFERASE ACTIVITY IN HUMAN ERYTHROCYTES. A PRESUMED TEST FOR HETEROZYGOUS CARRIERS OF THE GALACTOSEMIC DEFECT.

A simple, rapid, and direct method for measuring the activities of the galactokinase and Gal-1-P uridyl transferase enzymes in human erythrocytes is presented. The method has been applied to measurement of enzyme activities in a group of 37 presumably normal persons, 3 patients with galactosemia, 6 known heterozygous carriers of the defect, and 9 relatives of carriers. In every case the test unambiguously identified the individual's status as normal, heterozygotic carrier, or homozygously defective. Use of the test in genetic counseling and genetic epidemological studies is discussed.