MULTICOLOR FISH WITH A TELOMERE REPEAT AND SRY SEQUENCES SHOWS THAT SXR (SEX REVERSAL) IN THE MOUSE IS A NEW-TYPE OF CHROMOSOME REARRANGEMENT

XY(Sxr) (Sex reversal) mice carry a Y chromosome in which the chromati n (including Sry, the gene for testis determination) that normally res ides on the short arm is duplicated and the second copy is relocated t o the distal end of the long arm. Multicolor in situ hybridization to mitotic chromosomes of XY(Sxr) males using probes for the telomere rep eat sequence (TTAGGG)(n) and Sry shows that the rearranged chromatin i s located distal to the telomeric signal. This suggests that the rearr angement arose from a recombination event involving the distal Y telom ere sequences, i.e., within the telomere, a structure historically ass umed to be incapable of participating in chromosome rearrangements.