The concepts of sensitivity and resolution in the context of SNP-A–based karyotyping, metaphase cytogenetics, and FISH. (A) Numerically large clones characterized by a chromosomal defect are easily detectable by SNP-A (top portion). The presence of clonal mosaicism may be detected if individual clones reach the detection threshold. Compound defects (bottom portion) cannot be distinguished by SNP-A from clonal mosaicism (middle portion). (B) Comparison of sensitivity (size of the clone) and resolution (size of the lesion) between SNP-A, metaphase cytogenetics, and FISH.