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 and a probability of finding a single sequence of 0.75. It was characterized 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 fluorescent in situ hybridization (FISH) on chromosomes. Two linkage groups were newly assigned to chromosomes: LG2 to ECA3 and LG5 to ECA24, and five linkage groups were also oriented--LG3, LG4, LG5, LG8, and LG12--leaving only three groups unassigned. This work showed how this library makes an integrated map a realistic objective for the near future and how it can make comparative mapping more efficient in a search for candidate genes of interest.