Analysis of the sheep genome

Abstract

The identification of genes controlling several traits of interest in sheep has been accomplished by positional candidate cloning. In these studies, the trait is first mapped to a specific chromosomal region by linkage analysis, which requires families that are segregating for the trait and for polymorphic markers. Microsatellite markers are usually used for these analyses because of their extensive genetic variability. Once the location of a trait is determined by linkage to the markers, possible candidate genes controlling the trait can be inferred because of their proximity to linked markers. It is not necessary to map all possible genes in sheep for this strategy to be effective. Rather, a subset of genes that are mapped in humans and mice have also been mapped in sheep; these genes serve as "anchors" across the comparative maps of the different species. Further study of these positional candidates has revealed naturally occurring mutations that produce phenotypes that are unique to sheep. Thus the genetic analysis of sheep traits advances knowledge not only in this species but provides critical information for understanding biological pathways in mammalian species.

Polymorphisms of KAP6, KAP7, and KAP8 genes in four Chinese sheep breeds

“…According to their amino acid compositions, the wool matrix of KAPs are divided into three groups: the highsulfur proteins, the ultra-high-sulfur proteins, and the high-glycine-tyrosine proteins (HGTPs) (Cockett et al, 2001). The amount of protein from different groups varies both spatially and developmentally within the wool fiber (Powell and Rogers, 1990).…”

“…KAP genes are 0.6-1.5 kb in size and do not contain introns (Cockett et al, 2001). KAP7 and KAP8 are each coded by a single gene, whereas KAP6 is encoded by a multigene family (Kuczek and Rogers, 1987).…”

A genome-wide scan study identifies a single nucleotide substitution in ASIP associated with white versus non-white coat-colour variation in sheep (Ovis aries)

“…Pigmentation in domestic animals like sheep (including the wild population of Soay sheep) has been long considered to be tightly regulated by genetic variations in homologous genes identified in humans and model species (for example, Klungland et al, 2000;Andersson, 2001;Cockett et al, 2001;Sturm, 2006;Gratten et al, 2012). However, candidate gene approaches that are designed according to a priori hypotheses cannot evaluate the effect of the gene in the whole-genome context, nor can they identify other genes contributing to the phenotype.…”

“…The physical basis of variation in coat colour (and pattern) of domestic sheep (Ovis aries) is the ratio and amount of melanin (either eumelanin or pheomelanin) pigments produced in the cells of the wool follicles and transported into hair, skin and wool (see the review by Cockett et al (2001) and Deng et al (2009)). Domestication has changed the morphology as well as genetics associated with variations in coat pigmentation in sheep (Kijas et al, 2012).…”

COMPARATIVE ANALYSIS OF GENETIC MAPS OF Bos taurus L. AND Capra hircus L.

“…The comparison of genetic composition of individual chromosomes in different species was the subject of many studies (20)(21)(22)(23)(24)(25)(26)(27)(28), as well as phylogenetic analysis based on comparison of gene maps (29)(30)(31)(32). The comparison of chromosomal structure revealed divergent pathways in cytogenetic evolution of sheep species (33)(34)(35)(36)(37).…”