MOUSE CENTROMERE MAPPING USING OLIGONUCLEOTIDE PROBES THAT DETECT VARIANTS OF THE MINOR SATELLITE

Cytologically, the centromere is found at the very end of most Mus mus culus chromosomes, co-localizing with an array of minor satellite sequ ences. It is separated from the euchromatin of the long arm by a large domain of heterochromatin, composed in part of arrays of major satell ite sequences. We used oligonucleotide probes that specifically detect regions of sequence variation found in certain cloned minor satellite sequences. They detect a limited subset of the minor satellite arrays in the mouse genome, based on both pulsed-field gel electrophoresis a nd in situ hybridization data, and provide direct molecular genetic ma rkers for individual centromeres in some inbred mouse strains. Array s ize polymorphisms detected by these probes map to positions consistent with the centromeres of chromosomes 1 and 14 in the BXD recombinant i nbred (RI) strains. The genetic distances between these minor satellit e arrays and loci on the long arms of chromosomes 1 and 14 are consist ent with repression of meiotic recombination in the heterochromatic do mains separating them. The existence of chromosome-specific minor sate llite sequences implies that the rate of sequence exchange between non -homologous chromosomes relative to the rate between homologous chromo somes is much lower than has previously been postulated. We suggest th at the high degree of sequence homogeneity of mouse satellite sequence s may instead reflect recent common ancestry.