A GENOMIC CLONE CONTAINING A TELOMERE ARRAY MAPS NEAR THE CENTROMERE OF MOUSE CHROMOSOME-6

A lambda clone of mouse DNA containing a short array of telomere hexam ers has been localized by FISH to a region close to the centromere of Chromosome (Chr) 6. Amplification of DNA with primers flanking an SSR showed that most inbred strains carry one of two alleles, although fiv e other alleles were found among the inbred strains and 11 other allel es were found in wild-derived mice. Analysis of the DNA from four Robe rtsonian translocations suggests that the amplified sequence is still present in these chromosomes. The finding of two fragments associated with the Sig mutant suggests that the clone lies within a congenic reg ion created when the mutant, obtained in a (C3H x 101)F-1, was backcro ssed to C57BL/6J. This region might include all or part of the centrom ere. Comparison of the segregation of the amplification product with t he segregation of centromeric heterochromatin in an interspecies backc ross, (C57BL/6 x M. spretus)F-1 x M. spretus, (BSS) shows 1/72 recombi nants with the centromeric heterochromatin, while 1/62 recombinants oc curred in a BSB backcross. Analysis of other loci at the proximal end of Chr 6 gives the combined map 73-D6Mit86-0.73-D6Rp2-2.2-D6Mit1-2.2-W nt2-3.0-Cpa. Data from a third cross show that Cola2 lies between D6Mi t82 and D6Rp2. The portion of the telomere array, Tel-rs3, that has be en sequenced contains only 13/31 repeats of the consensus sequence. A variety of sequence changes from the consensus hexamer suggests that t his array has been removed for a long time from evolutionary pressures to retain the TTAGGG sequence.