2 MOUSE HYPERVARIABLE MINISATELLITES - CHROMOSOMAL LOCATION AND SIMULTANEOUS MUTATION

Pc-1 and Pc-2 hypervariable minisatellites of the mouse show a structu ral similarity and hence have been compared in terms of chromosomal lo cation and mutability. Polymorphisms of the Pc-2 locus detected by ana lyses of Southern blotting and polymerase chain reaction were used for typing 61 backcross mice that were obtained by mating (C57BL/6 X MSM) F1 females to MSM males. Segregation patterns indicated that the Pc-2 locus maps to the 60 cM region of chromosome 6, while that of Pc- 1 ma ps to chromosome 4. Simultaneous mutation of the two loci was examined in 101 F1 mice. Pc-1 and Pc-2 loci showed mutation rates of 14.4 and 5.0% per gamete, respectively. Of the nine mice with a Pc-2 mutation, four carried a Pc-I mutation at the same maternally- or paternally-der ived allele. The rate of comutation was 44% (4/9), higher than the 12. 2% (24/197) of Pc-1 mutation alone. This suggests that the germline mu tation of the two hypervariable minisatellites may result from a commo n mechanism.