Molecular karyotyping of the patient and his parents. (A) GTG-banding and FISH analysis of homologous chromosomes 4 in proband, mother and father. The chromosomes are counterstained with DAPI (blue). The proximal flanking BAC RP11-188P17 is labeled with fluorescein-dUTP (green) and the deleted BAC RP11-775P18 with rhodamine-dUTP (red). An arrowhead indicates the critical band q35.1q35.2 on the patient’s derivative chromosome. (B) Illumina SNP array analysis (B allele frequency and log R ratio) of the 4q35.1q35.2 region in the boy with terminal 4q deletion syndrome. (C) Selected genotypes in the deletion interval from the Illumina array are depicted for proband (left), mother (middle), and father (right). Mendelian transmission errors (absence of maternal genotypes) in the proband are indicated in gray.