LOCATION OF THE 9257-MUTATION AND ATAXIA MUTATION ON MOUSE CHROMOSOME-18

The location of three mutations on proximal Chromosome (Chr) 18 was de termined by analysis of the offspring of several backcrosses. The resu lts demonstrate that ataxia and the insertional mutation TgN9257Mm are separated by less than 1 cM and are located approximately 3 cM from t he centromere, while the balding locus is 7 cM more distal. Previous d ata demonstrated that the twirler locus also maps within 1 cM of ataxi a. The corrected locations will contribute to identification of approp riate candidate genes for these mutations. Two polymorphic microsatell ite markers for proximal Chr 18 are described, D18Umil and D18Umi2. Th e Lama3 locus encoding the alpha 3 subunit of nicein was mapped distal to ataxia and did not recombine with Tg9257.