Gene mapping from a bovine 1;29 DNA library prepared with chromosome microdissection.

Bovine gene mapping is progressing rapidly using syntenic group mapping based on somatic cell hybrids and linkage, and to a lesser extent on in situ hybridization. Single chromosome DNA libraries are a logical next step, and this was, therefore, the aim of our laboratory. Since we have access to several cattle with t(1;29) and this chromosome is readily distinguishable, we chose this as our first target--recognizing that we would not produce a "single" chromosome library in the strict sense because two autosomes are represented. We utilized an inverted microscope and a micromanipulator fitted with glass instruments pulled specifically to dissect off approximately 100 t(1;29) chromosomes per microdrop. A glass chamber made to accommodate a hanging drop was used to extract the DNA under a dissecting microscope. The DNA was then cleaved with EcoRI and inserted in lambda gtwes arms. Host cells were then infected with these phage and positive clones obtained. The first clone, isolated from this library by hybridization with a human collagen 6A1 cDNA, was mapped by in situ hybridization to bovine Chromosome some (Chr) 1q12-q14, near the centromere. The second clone, an anonymous DNA fragment (D1S11), was mapped to 1q43-q46, near the terminal end.