EXPERIMENTAL FIGURE 8-6 Simple-sequence DNA is localized at the centromere in mouse chromosomes. Purified simple-sequence DNA from mouse cells was copied in vitro using E. coli DNA polymerase I and fluorescently labeled dNTPs to generate a fluorescently labeled DNA “probe” for mouse simple-sequence DNA. Chromosomes from cultured mouse cells were fixed and denatured on a microscope slide, and the chromosomal DNA was then hybridized in situ to the labeled probe (light blue). The slide was also stained with DAPI, a DNA-binding dye, to visualize the full length of the chromosomes (dark blue). Fluorescence microscopy shows that the simple-sequence probe hybridizes primarily to one end of the telocentric mouse chromosomes (i.e., chromosomes in which the centromeres are located near one end).

[Courtesy of Sabine Mal, Ph.D., Manitoba Institute of Cell Biology, Canada.]