Use of a polymorphic dinucleotide repeat sequence to detect non-blastomeric contamination of the polymerase chain reaction in biopsy samples for preimplantation diagnosis

Using the polymerase chain reaction (PCR), amplification oftwo different target DNA sequences has been achieved with highfrequency using single human blastomeres as template for theduplex reaction. One sequence is located within the –globingene and contains the sickle cell locus, the other is a polymorphicdinucleotide repeat, which, as well as acting as a positivecontrol for amplification, was used to check the origin of theamplified DNA. A comparison of the sequences amplified fromthe blastomere with sequences amplified from parental samplesconfirmed that amplification of blastomeric sequences, but notextraneous contaminating DNA, had taken place in most cases.The efficacy of this system for detecting extraneous DNA waschecked by deliberately contaminating single blastomeres withforeign cells. The presence of contamination was detected bythe amplification of sequences not present in blastomeric DNAand which therefore must have been amplified from extraneouscontaminating DNA.