SNP array analysis of paired BM and fibroblast DNAs distinguishes between constitutional homozygosity and acquired UPD. (A) Large chromosomal regions of constitutive homozygosity were detected by SNP array in the DNAs of a male FA patient with a degree of consanguinity (patient EGF067, top panel) but not in a male heterozygote composite FA patient (patient EGF074, bottom panel). Homozygosity regions were detected by comparison with a HapMap reference set; fibroblast and BM DNA analyses are shown on the left and on the right of each chromosome ideogram, respectively. The location of the FANCA gene at 16q24 is shown. Chromosome 13, which harbors both a constitutive homozygosity region in fibroblast (left) and a larger acquired UPD in the BM only (right), is boxed. (B) Enlargement of chromosome 13 data from patient EGF067. Heterozygous (AB) and homozygous (AA and BB) calls and copy number data are indicated. The short constitutive copy-neutral region of homozygosity in fibroblasts (left) and the larger acquired UPD (copy-neutral loss of heterozygosity) in BM (right) are boxed. Analysis was performed from Affymetrix SNP array data with the Partek software.