A second-generation linkage map of the sheep genome

Area of Science:

• Genomics and genetics
• Comparative genomics
• Livestock breeding

Background:

• Development of high-density genetic maps is crucial for understanding genome organization and facilitating genetic improvement in livestock.
• Comparative mapping between species like sheep and cattle can leverage existing genomic resources and accelerate gene discovery.

Purpose of the Study:

• To construct a high-density genetic map for sheep (Ovis aries) utilizing microsatellite markers.
• To compare the sheep genetic map with the established cattle (Bos taurus) linkage map to assess genomic conservation.
• To explore the utility of conserved marker order for quantitative trait loci (QTL) mapping in both species.

Main Methods:

• Genotyping of 519 markers (504 microsatellites) in sheep populations (IMF and USDA flocks).
• Integration of genotypic data to construct linkage groups and estimate map distances (cM).
• Comparative analysis of marker order and synteny with the USDA-ARS MARC cattle linkage map.

Main Results:

• A sheep genetic map spanning approximately 3063 cM (autosomes) and 127 cM (X chromosome) was developed.
• Seventy-three percent of sheep microsatellite markers were common with the cattle map, exhibiting conserved marker order across homologous linkage groups.
• A specific translocation event involving ovine chromosome 9 was identified, consistent with previous findings in cattle.

Conclusions:

• The high degree of genomic conservation between sheep and cattle linkage maps facilitates cross-species comparative genomics.
• The established sheep genetic map provides a valuable resource for identifying genes underlying economically important traits.
• Leveraging conserved synteny will accelerate the discovery of quantitative trait loci (QTLs) in both sheep and cattle.