Interestingly, in the DGS/VCFS group the loss of replication asynchrony observed for the SNRPN locus is mainly due to an advanced replication of the normally late-replicating (maternal) allele, while the loss of asynchrony for SNRPN in the Williams syndrome patients is mostly associated with a delay in the replication timing of the normally early-replicating (paternal) SNRPN allele. The gene discussed is SNRPN; the disease is Williams syndrome.