The possibility of prenatal diagnosis by gene dosage: Confirmation of duplication 10q24→qter from Got‐l activity in fetal erythrocytes

The activity of four enzymes, including GOT‐1, has been investigated in the erythrocytes of a 10q→24qter trisomic fetus. Analyses have been performed on a feto‐maternal blood mixture sampled by fetoscopy and on red cells obtained by cardiac puncture, following therapeutic abortion. The demonstration of a 40 percent increase of GOT‐1 activity, as compared to normal fetuses of similar gestational age, suggests that gene dosage studies may be a useful confirmatory technique in prenatal diagnosis of unbalanced chromosomal aberrations. Practical application of a similar diagnostic approach is conditioned by (1) precise characterization of fetal chromosome imbalance; (2) confirmed assignment of the gene locus coding for the gene product under investigation; (3) evidence of a linear proportionality between gene dose and concentration of the gene product in patients with the same chromosome imbalance detected in the fetus; (4) knowledge of the range of normal variation at different weeks of gestation of the enzyme activity to be tested in the fetus; (5) safety of fetal sampling procedure.