Figure 3

Oligonucleotide microarray analysis of artificially derived mosaic trisomy 21 samples. (A) 10% trisomy 21 showing a very subtle copy-number gain for all clones on chromosome 21. The profile was generated using DNA extracted from a mixture of blood which contained 10% WBCs from a trisomy 21 subject and 90% WBCs from a normal male individual. (B) 15% trisomy 21, generated as in (A), showing a very subtle copy-number gain for all clones on chromosome 21. (C) 20% trisomy 21, generated as in (A) showing a subtle copy-number gain for all clones on chromosome 21. (D) 30% trisomy 21, generated as in (A), showing a clear copy-number gain for all clones on chromosome 21. The inset images to the right of each array plot show the average log₂ ratio of all probes mapping to chromosome 21, with the horizontal dotted line representing a log₂ ratio of zero and the vertical dotted line representing the centromere. A pink bar plotted above the horizontal line represents a copy-number gain of all probes on chromosome 21. To the left of each inset image is the average log₂ ratio at the specified proportion of trisomic cells.