An Enhanced Linkage Map of the Sheep Genome Comprising More Than 1000 Loci

Abstract

A medium-density linkage map of the ovine genome has been developed. Marker data for 550 new loci were generated and merged with the previous sheep linkage map. The new map comprises 1093 markers representing 1062 unique loci (941 anonymous loci, 121 genes) and spans 3500 cM (sex-averaged) for the autosomes and 132 cM (female) on the X chromosome. There is an average spacing of 3.4 cM between autosomal loci and 8.3 cM between highly polymorphic [polymorphic information content (PIC) Ն 0.7] autosomal loci. The largest gap between markers is 32.5 cM, and the number of gaps of >20 cM between loci, or regions where loci are missing from chromosome ends, has been reduced from 40 in the previous map to 6. Five hundred and seventy-three of the loci can be ordered on a framework map with odds of >1000 : 1. The sheep linkage map contains strong links to both the cattle and goat maps. Five hundred and seventy-two of the loci positioned on the sheep linkage map have also been mapped by linkage analysis in cattle, and 209 of the loci mapped on the sheep linkage map have also been placed on the goat linkage map. Inspection of ruminant linkage maps indicates that the genomic coverage by the current sheep linkage map is comparable to that of the available cattle maps. The sheep map provides a valuable resource to the international sheep, cattle, and goat gene mapping community.Sheep play an important role in modern agriculture and possess many heritable traits that are of economic importance. Additionally, the size, physiology, temperament, and lifespan of sheep make them an appropriate model for studying a variety of mammalian biological functions including lung physiology, immunology, endocrinology, reproduction, embryology, and fetal development. Sheep are also useful as disease models for inherited diseases, such as asthma (Wright et al.

Conservation genetics in Chinese sheep: diversity of fourteen indigenous sheep (Ovis aries) using microsatellite markers

“…1997; Maddox et al. 2001 and FAO 2011) that were suggested for biodiversity studies in sheep (Table 2). The methods of DNA extracted and the PCR protocols reference as Zhong et al.…”

Examination of a region showing linkage map discrepancies across sheep breeds

“…The advent of molecular markers has seen the construction of linkage maps for a variety of commercially important livestock species including cattle (Barendse et al 1997; Kappes et al 1997; Ihara et al 2004), chicken (Groenen et al 2000; Schmid et al 2000), deer (Slate et al 2002), pig (Archibald et al 1995;Rohrer et al 1996), and sheep (de Gortari et al 1998; Maddox et al 2001). The primary purpose of such linkage maps is to provide a framework to locate genes of commercial importance, either through linkage mapping or comparative analysis.…”

A presentation of the differences between the sheep and goat genetic maps

“…The methods used for all aspects of map construction of the sheep genetic map are described in [17]. The current version (4.2) best positions sheep genetic map [3] was aligned with the most recent goat linkage map [23].…”

“…1). Other features of gross chromosomal morphology, such as the architecture of the X chromosome and that of OAR 9/CHI 14, are similar for sheep and goats, but differ from cattle [7,11,14,17,22,27]. The similarity between the goat and sheep karyotypes is further evidenced by reports of natural matings between rams and does producing hybrid offspring, with at least one instance of such a mating generating a female offspring that was shown to be fertile when mated to a ram [16,24,25].…”