A cosmid specific for sequences encoding a microtubule-associated protein, MAP1B, contains a polymorphic microsatellite and maps to bovine chromosome 20q14.

A clone for the bovine gene MAP1B was isolated from a bovine cosmid library with a probe obtained by cross-species PCR. The single positive cosmid clone was localized by FISH to chromosome region 20q14. Analysis of the cosmid revealed the presence of a microsatellite motif with a two-allele polymorphism detectable by PCR amplification of genomic DNA. However, the analysis of this polymorphism in a bovine family affected by SMA indicated absence of very close linkage of the phenotype for bovine SMA with MAP1B.