AN INTERSTITIAL TELOMERE ARRAY PROXIMAL TO THE DISTAL TELOMERE OF MOUSE CHROMOSOME-13

Lambda clones of mouse DNA from BALB/c and C57BL/10, each containing a n array of telomere hexamers, were localized by FISH to a region close to the telomere of Chr 13. Amplification of mouse genomic DNA with pr imers flanking SSRs within the cloned DNA showed several alleles, whic h were used to type eight sets of RI strains. The two lambda clones co ntained allelic versions of the interstitial telomere array, Tel-rs4, which is 495 bp in C57BL/10 and which includes a variety of sequence c hanges from the consensus telomere hexamer. Comparison of the segregat ion of the amplification products of the SSRs with the segregation of other loci in an interspecies backcross (C57BL/6JEi x SPRET/Ei) F-1 x SPRET/Ei shows recombination suppression, possibly associated with rib osomal DNA sequences present on distal Chr 13 in Mus spretus, when com pared with recombination in an interstrain backcross, (C57BL/6J x DBA/ J) F-1 x C57BL/6J, and with the MIT F-2 intercross. Analysis of recomb ination in females using a second interstrain backcross, (ICR/Ha x C57 BL/6Ha) F-1 x C57BL/6Ha, also indicates recombination suppression when compared with recombination in males of the same strains, using backc ross C57BL/6Ha x (TCR/Ha x C57BL/6Ha) F-1. Thus, more than one cause m ay contribute to recombination suppression in this region. The combine d order of the loci typed was D13Mit37-D13Mit30-D13Mit148 (D13Rp1, 2, 3, 4, Tel-rs4)-D13Mit53-D13Mit196-D13Mit77- (D13Mit78, 35). Data from crosses where apparently normal frequencies of recombination occur sug gest that the telomere array is about 6 map units proximal to the most distal loci on Chr 13. This distance is consistent with evidence from markers identified in two YAC clones obtained from the region.