SNP markers and their use in sheep breeding

Domestic sheep (Ovis aries) is one of the first domesticated livestock species, which, following human migrations, spread to most countries around the world. The modern sheep gene pool is represented by a vast variety of breeds, differing in wool type (fine wool, semi-fine wool, semi coarse wool, and coarse wool) and tail type (short/long, fat/thin). DNA microarrays have revolutionized the area of genomic research of domestic sheep and their wild relatives, allowing the identification of signatures of selection that shaped the genomes of existing breeds. Certain signatures of selection have been identified in most breeds and contain so called selection hotspots"— genomic regions containing genes primarily associated with growth and development, body size, and coat color. Candidate genes involved in the formation of adaptations are identified in genomic regions that underlie selection pressure in local breeds living in extreme conditions. This review summarizes the results of studies examining the origins of local sheep breeds in relation to the global gene pool, represented by whole genome SNP genotypes from publicly available databases. A brief description of the main modern bioinformatics approaches used to search for signatures of selection is provided. Key candidates associated with economically significant traits, disease resistance, adaptive qualities, and phenotypic characteristics are listed. Assessing genomic diversity in sheep populations is important not only for generating new knowledge on their origins but also for developing approaches for preserving valuable genotypes.

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