The Cenpj hypomorphic mouse (Cenpjtm/tm) that we have created displays many of the classical clinical features of Seckel syndrome, including intrauterine and postnatal dwarfism, microcephaly, a sloping forehead, neuropathogical abnormalities, memory impairment and genomic instability [1], [4], [7], [15], [28], [63]. This evidence concerns the gene CPAP and microcephaly.