In vivo visualization of chromosomes using lac operator-repressor binding

This article describes a new technique for direct, in vivo visualization of chromosome dynamics based on lac repressor recognition of direct repents of the lac operator. The method allows the tagging of specific chromosomal sites and thus in situ localization with minimal perturbation of structure. Detection by light microscopy, using GFP-repressor fusion proteins or immunofluorescence, can be complemented by higher-resolution electron microscopy using immunogold staining. Applications of this method will facilitate the investigation of interphase chromosome dynamics, as well as chromosome segregation during cell division in organisms that lack cytologically condensed chromosomes.