A comparison of array CGH and SNP array results for chromosome 20 from 26 day old bone marrow. Bone marrow was refrigerated for 26 days before DNA extraction. Deletion, gain or amplification of different regions of 20q, and low level gain of 20p have been extensively validated by single locus FISH, G-banding, M-BAND and M-FISH (Case SVH01, ). Duplicate experiments were performed, and two 0.2 Mb moving average lines are shown for the array CGH specimen to show the peaks of localized amplification. The probes in the custom Agilent array are spaced between 200 bp and 9 kb apart (see Figure 1) and the Illumina CytoSNP 12 array probes have a median spacing of 6.1 kb.