Development of a Linkage Map and Mapping of Phenotypic Polymorphisms in a Free-Living Population of Soay Sheep (Ovis aries)

Abstract

An understanding of the determinants of trait variation and the selective forces acting on it in natural populations would give insights into the process of evolution. The combination of long-term studies of individuals living in the wild and better genomic resources for nonmodel organisms makes achieving this goal feasible. This article reports the development of a complete linkage map in a pedigree of free-living Soay sheep on St. Kilda and its application to mapping the loci responsible for three morphological polymorphisms for which the maintenance of variation demands explanation. The map was derived from 251 microsatellite and four allozyme markers and covers 3350 cM ($90% of the sheep genome) at $15-cM intervals. Marker order was consistent with the published sheep map with the exception of one region on chromosome 1 and one on chromosome 12. Coat color maps to chromosome 2 where a strong candidate gene, tyrosinase-related protein 1 (TYRP1), has also been mapped. Coat pattern maps to chromosome 13, close to the candidate locus Agouti. Horn type maps to chromosome 10, a location similar to that previously identified in domestic sheep. These findings represent an advance in the dissection of the genetic diversity in the wild and provide the foundation for QTL analyses in the study population.

The evidence of associations between prion protein genotype and production, reproduction, and health traits in sheep

“…A total of 51 QTL are described in the sheep database "SheepQTLdb" 9 ; 2 of these are associated with immune function, 21 with parasite resistance, 1 with skeletal abnormality, 4 with coat colour, 2 with fibre, 9 with fleece, 1 with mastitis, 2 with milk protein, 8 with reproduction, and 1 with horn growth. Two of these QTL are located on chromosome 13 -both are associated with coat pattern and are in proximity to the Agouti locus [9]. A further QTL has recently been identified on chromosome 13 that is associated with wool fibre diameter (at 110 cM) and another that is indirectly associated with resistance to Salmonella infection (at 36 cM) [85].…”

Extensive linkage disequilibrium in a wild bird population

“…Among the most important applications of genetic maps in genomic analyses is in that they provide a platform to support studies utilizing or aiming to apply candidate gene approaches [21,23], QTL mapping [24], comparative genomics [25], and genome annotation [26]. However, construction of genetic linkage maps for non-model organisms is complicated by several factors [27,28].…”

Genetic background of coat colour in sheep

“…The ovine agouti locus has been mapped to chromosome 13, containing the sequence for the agouti signaling protein (Beraldi et al, 2006). The ASIP variations include a nine base pair deletion (D9) g.10-19delAGCCGCCTC, a five base pair deletion (D5) g.100-105delAGGAA, and point mutations: g.5051G > C and g.5172T > A.…”