Amplification of 836-bp fragment across the deletion. P1 and P2 are genomic DNA from the 2 patients, C1-C6 are control DNAs, H18 and H9 are haploid hybrids containing the deletion, H5 and H22 are the hybrids containing the undeleted allele, M is a PhiX174/HaeIII size marker, and B is the negative control.