Confirmation and segregation by endonuclease restriction digestion of mutations presumed to represent incidental findings. The upper gel shows restriction digestion using the HphI restriction enzyme for the p.G608D mutation in ABCD1, causative for adrenoleukodystrophy (ALD). All tested individuals, none of which presented with ALD, are shown to be heterozygous for the mutation, including all males whom are hemizygous for genes on the × chromosome. The lower gel shows restriction digestion using the BtgI restriction enzyme for the p.T879K mutation in IGHMBP2, putatively causative for spinal muscular atrophy with respiratory distress type 1 (SMARD1). Random segregation and zygosity for this variant can be observed in this family; none of the individual subjects present with SMARD.