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 of two differ ent target DNA sequences has been achieved with high frequency using s ingle human blastomeres as template for the duplex reaction. One seque nce is located within the beta-globin gene and contains the sickle cel l locus, the other is a polymorphic dinucleotide repeat, which, as wel l as acting as a positive control for amplification, was used to check the origin of the amplified DNA, A comparison of the sequences amplif ied from the blastomere with sequences amplified from parental samples confirmed that amplification of blastomeric sequences, but not extran eous contaminating DNA, had taken place in most cases. The efficacy of this system for detecting extraneous DNA was checked by deliberately contaminating single blastomeres with foreign cells. The presence of c ontamination was detected by the amplification of sequences not presen t in blastomeric DNA and which therefore must have been amplified from extraneous contaminating DNA.