Use of cosmid-derived and chromosome-specific canine microsatellites

The majority of microsatellite markers being used to generate the emerging genetic linkage maps of the dog are derived from small-insert, random clone s. While such markers are easy to generate, they have the disadvantage that they cannot easily be physically mapped by fluorescence in situ hybridizat ion (FISH), making it difficult to assess the extent of genome coverage rep resented by such maps. In contrast, microsatellite markers from large-inser t libraries enable the linkage groups within which they fall to be physical ly anchored to specific chromosomes. One aim of our work is to identify at least one microsatellite-containing cosmid clone for each canine chromosome , to ensure that linkage groups exist for all chromosomes. This is particul arly important for a species with as complex a karyotype as the dog. Locati ng two cosmids on each chromosome would allow the orientation of the linkag e groups to be established, Chromosomal locations of cosmid clones containi ng microsatellites have been determined by FISH and confirmed using canine chromosome-specific paints. Microsatellite sequences have been genotyped on the DogMap reference family. Microsatellites derived from flow-sorted, chr omosome-specific libraries represent another source of useful markers. Init ial studies have been carried out on the canine X chromosome, on which mark ers were underrepresented in our initial studies.