Abstract
Several quantitative trait loci (QTL) for important reproductive traits (ovulation rate) have been identified on the porcine chromosome 15 (SSC15). To assist in the selection of positional candidate swine genes for these QTL on SSC15, twenty-one genes had already been assigned to SSC15 in a previous study in our lab, by using the radiation hybrid panel IMpRH. Further polymorphism studies were carried out on these positional candidate genes with four breeds of pigs (Duroc, Erhualian, Dahuabai and Landrace) harboring significant differences in reproduction traits. A total of nineteen polymorphisms were found in 21 genes. Among these, seven in six genes were used for association studies, whereby NRP2 polymorphism was found to be significantly (p < 0.05) associated with litter-size traits. NRP2 might be a candidate gene for pig-litter size based on its chromosome location (Du et al., 2006), significant association with litter-size traits and relationships with Sema and the VEGF super families.
Highlights
More than 1800 quantitative trait loci (QTL) had already been mapped on the entire pig genome until June 3rd, 2008, based on statistics available in the Pig QTL Database
At least one polymorphism was identified in 11 genes (COL4A4, DPP4, EPHA4, HES6, HSPE1, KCNJ3, NRP2, ORC2L, SH3BP4, SP3 and TRIP12) among the 21 genes analyzed
We identified 19 polymorphic positions in the total contig length of 8 943 bp, corresponding to an overall average of one polymorphism per 470 bp
Summary
More than 1800 quantitative trait loci (QTL) had already been mapped on the entire pig genome until June 3rd, 2008, based on statistics available in the Pig QTL Database. The step would be to identify candidate genes for these traits by developing a detailed comparative map and a SNP map that would both constitute an effective method for assisting in the selection of the underlying genes responsible for the mapped QTL. A QTL affecting meat quality in chromosome 2p has already been well described (Andersson-Eklund et al 1998; Knott et al 1998; de Koning et al 1999), these methods being essential in the identification of regulatory mutation in the causal gene IGF-2 (Jeon et al 1999; Nezer et al 1999; de Koning et al 2000; Nezer et al 2003; Van Laere et al 2003). A straightforward strategy for the identification of SNP is locus-specific amplification (LSA) and comparative re-sequencing from multiple indi-
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