FISHdetection oftrisomy 21ininterphase by thesimultaneous useoftwodifferentially labelled cosmid contigs

Techniques havebeenreported inwhich fluorescence insituhybridisation (FISH) andcosmidprobesareusedtodetect trisomy21 (andotherabnormalities involving chromosomesX,Y,13,and18) onuncultured amniocytes. Howeverthe detection rateoftrisomy 21islowerthan fortheotheranomalies owingtoalarger number ofuninformative results and false negatives. We reportthesimultaneous useoftwo differentially labelled cosmidcontigs to improvethedetection rateoftrisomy21 on uncultured amniocytesamplesthus allowing theprenatal diagnosis ofDown's syndrome evenifonlyfewlabelled nuclei areavailable.