Fig. 2.

Results of Chromosomal Microarray in Case 1. Smooth signal is plotted at 2, indicating that two copies of the chromosome 15q arm are present without any deletion or duplication of the Prader-Willi/Angelman syndrome critical region. Allele peaks show the genotype calls. Genotype calls and allele dosage normalization are performed as follows: the formula for allele peaks is A – B, where A is the signal of the A allele and B is the signal of the B allele. The allele peaks are normalized such that AA = 1, AB = 0, and BB = −1. Therefore, the absence of heterozygosity would be observed as loss of the AB allele peaks (plotted at 0) with only AA (plotted at 1) and BB (plotted at −1) allele peaks present, as shown with case 1