Gene mapping in cattle has progressed rapidly in recent years largely owing to the introduction of powerful genetic markers, such as the microsatellites, and through advances in physical mapping techniques such as synteny mapping and fluorescence in situ hybridization (FISH). Microsatellite markers are often not physically mapped because they are generally isolated from small insert plasmid libraries, which makes their chromosomal localization inefficient. In this report we describe the FISH mapping of a large group of cosmid-derived bovine microsatellite markers, as our contribution to the European mapping initiative, BovMap. One objective of BovMap is to develop a set of anchored loci for the cattle genome map. Two cosmid libraries were screened with probes corresponding to the (AC)n microsatellite motif. Positive clones were mapped by FISH, and then a subset was further analyzed by sequencing the region flanking the microsatellite repeat. In total, 58 clones were hybridized with chromosomes and identified loci on 22 of the 31 different bovine chromosomes. Three clones contained satellite DNA. Two or more markers were placed on 12 chromosomes. Sequencing of the microsatellites and flanking regions was performed directly from 43 cosmids, as previously reported (Ferretti et al. Anim. Genet. 25, 209-214, 1994). Primers were developed for 39 markers and used to describe the polymorphism associated with the corresponding loci.

Summary Silver staining was used to detect amplified microsatellite loci from the bovine genome. The standard silver‐staining procedure was modified to allow more direct control in the development of signals. Microsatellites were analysed, to compare the silver‐staining technique and the direct incorporation of a radioactive tracer. With silver staining, levels of sensitivity were achieved that are typical of those with radioisotopic detection. Also, silver staining is a cheaper process, is less hazardous to operators and the environment, and can be performed in laboratories without radioisotopic facilities. A significant advantage of silver staining is the speed of the process, producing results of a typing in 1 day. Zusammenfassung Charakterisierung von Rinder Mikrosatelliten durch Silberfärbung Mit Silverstaining (Silberfärbung) wurden amplifizierte Mikrosatellite von Rindern verschiedener Rassen charaktisiert. Für drei Mikrosatelliten wurden einige Nanogramme genomische DNA amplifiziert. Diese Technik erwies sich als empfindlicher und einfacher als die radioisotopische Methodologie und ist auch billiger und ungefährlicher für Forscher und Umwelt. Kann innerhalb eines Tages Ergebnisse erreicht werden Letztens, kann diese Tecknik für Forschung in Labors gebraucht werden, wo keine Radioaktivität benutzt werden kann.