Detection by electron microscopy of a small subband 13q14.11 deletion in an hereditary retinoblastoma

High-resolution banding, specific for electron microscopy, was applied to chromosomes of synchronized blood lymphocytes obtained from a child with bilateral retinoblastoma. Ultrastructural analysis of the subbands in region q14.1, after synchronization and immunochemical banding, showed that the deletion in the abnormal chromosome 13 corresponds to subband 14.11, thus evidencing that the retinoblastoma gene is located within subband q14.11. This first application to a diagnostic problem of immunochemical banding suggests that, coupled with electron microscopy, this banding provides a higher resolution than that obtained with light microscopy and should be useful to pinpoint important localizations.