Use of a biotinylated DNA probe specific for the human Y chromosome for rapid antenatal sex determination

We have cloned a male-specific 3.4 kb human DNA sequence which showed only little crosshybridisation to autosomal sequences. To further enhance the specificity of the probe, we subcloned an internal TaqI-fragment resulting in clone pH343T33. This clone was used to determine the presence of Y-chromosomal sequences in DNA extracted from amniotic cells and from chorionic villi by Southern and dot hybridisation assays, respectively. Using this clone, we correctly predicted fetal sex in all of 148 cases analysed. To facilitate the use of this clone in clinical practice, we simplified the dot hybridisation procedure so that it can be performed in less than 48 h. The procedure with 32P-labeled DNA probes requires less than 0.5 mL of amniotic fluid; when biotinylated DNA probes are used, 3-5 mL of amniotic fluid usually suffice. We have used this probe in genetic counseling of families at risk for X-linked disorders.