PCR based detection of trisomy 18 and trisomy 21 compared against results obtained by CGH microarrrays in Preimplantation Genetic Screening Overall design: Three-condition experiment: subjects classified by results from PCR as lacking trisomies in either chromosome 18 or 21 were labeled "non-trisomy". If a trisomy was otherwise present and detected by PCR, subjects were labeled "trisomy 18" or "trisomy 21". These classifications were then matched against the results of CGH. Biological replicates: 9 "non-trisomy" embryos, 5 "trisomy 18" embryos and 7 "trisomy 21" embryos. Please note that the row counts for the raw data files vary from 2,101 to 2,878. Even with the standard protocol according Illuminas 24sure instructions for the microarrays, each run generates a set of analyzed probes that varies from sample to sample. However all the different combinations represent a uniform sampling of the genome.