CONSTRUCTION OF A HORSE BAC LIBRARY AND CYTOGENETICAL ASSIGNMENT OF 20 TYPE-I AND TYPE-II MARKERS

A horse BAC library was constructed with about 40, 000 clones and mean insert size of 110 kb representing a 1.5 genome equivalent coverage a nd a probability of finding a single sequence of 0.75. It was characte rized by PCR screening of about 130 sequences of horse microsatellites and exonic gene sequences retrieved from databases. BACs containing 8 microsatellites and 12 genes were subsequently localized by fluoresce nt in situ hybridization (FISH) on chromosomes. Two linkage groups wer e newly assigned to chromosomes: LG2 to ECA3 and LG5 to ECA24, and fiv e linkage groups were also oriented-LG3, LG4, LG5, LG8, and LG12-leavi ng only three groups unassigned. This work showed how this library mak es an integrated map a realistic objective for the near future and how it can make comparative mapping more efficient in a search for candid ate genes of interest.