Amplification of X- and Y-chromosome-specific regions from single human blastomeres by polymerase chain reaction for sexing of preimplantation embryos.

We describe a polymerase chain reaction (PCR) assay for the simultaneous detection of X and Y chromosomes in human blastomeres. In a first round of PCR, both X- and Y-specific fragments are amplified with primers which are common to both chromosomes and are derived from the X-linked steroid sulphatase gene and the Y-linked pseudogene. In a second round of PCR, fragments specific to each chromosome are generated: both an X and a Y fragment in male embryos and, due to the absence of a Y chromosome, only an X fragment in females. The efficiency and accuracy of this assay are high; it generates no false positive amplification signals and allows sexing in approximately 6 h after embryo biopsy. We therefore believe that it is suitable for gender determination by preimplantation diagnosis for couples at risk for X-linked genetic diseases.