Sequential immunocytogenetics, molecular cytogenetics and transmission electron microscopy of microspread meiosis I oocytes from a human fetal carrier of an unbalanced translocation

The oocytes of a 17 week human fetus carrying an unbalanced 46,XX,add(18)(p13) translocation were studied with a sequential combination of microspreading, immunocytogenetics, fluorescence in situ hybridization (FISH) and transmission electron microscopy. This combination of technologies allowed the collection of data of unique accuracy and resolution. The translocated chromosome was found to be involved in five different synaptic configurations. A consistent feature of these configurations was the involvement of a second small bivalent, presumably chromosome 21 or 22, the normal synapsis of which was often disrupted. We conclude that chromosome 21 or 22 was the source of the translocated material, which was found to be either homologously triply synapsed, heterologously synapsed or asynapsed.