Mouse chromosome translocations: visualization and analysis by electron microscopy of the synaptonemal complex

Pachytene chromosomes of mice heterozygous for known translocations are clearly depicted by configurations of the synaptonemal complexes in spread (whole mount) preparations. In one autosomal and two X-autosome translocations analyzed, breakpoints are identifiable; localization by measurement agrees with mitotic data and shows the translocations to be reciprocal. Synapsis with the Y is inhibited in one translocation in which the breakpoint is the pairing region of the X.