A recombinant DNA probe was used for antenatal sex determination. The probe was isolated from the 3.4 kilobase human repeat sequence derived from heterochromatin of the Y chromosome and had 1000 times more affinity for male DNA than for female DNA. A dot blot hybridisation method with 200 microliter of amniotic fluid yielded accurate results in 2 to 3 days. This test should facilitate antenatal diagnosis of sex-linked genetic disorders.
