2010-Boysen_et_al - Detection of a quantitative trait locus...

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T. J. Boysen, J. Tetens and G. Thaller population 2 the ortholog of the callipyge locus in an experimental pig F Detection of a quantitative trait locus for ham weight with polar overdominance near doi: 10.2527/jas.2009-2565 originally published online June 25, 2010 2010, 88:3167-3172. J ANIM SCI http://jas.fass.org/content/88/10/3167 the World Wide Web at: The online version of this article, along with updated information and services, is located on www.asas.org by guest on October 10, 2011 jas.fass.org Downloaded from
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ABSTRACT: The distal part of SSC7, which con- tains the ortholog to the ovine region encompassing the callipyge locus, was analyzed in a Piétrain F 2 re- source population comprising more than 2,700 off- spring. The aim of the study was to map QTL affecting carcass traits comparable with the callipyge phenotype in sheep. We applied an interval mapping approach using 14 microsatellite markers and detected 3 QTL with small effects. The first QTL affects fat thickness on the middle of the back, with no detectable impact on fat sizes at other places on the back, whereas the second QTL affects side fat thickness. The third QTL influences the ham weight and shows a clear parent-of- origin-dependent effect in the form of maternal polar overdominance. It is not located at the position of the imprinting cluster including the callipyge locus, but 7 cM proximal. Key words: callipyge, ham, imprinting, pig, quantitative trait locus ©2010 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2010. 88:3167–3172 doi:10.2527/jas.2009-2565 INTRODUCTION In diploid organisms, gene expression of the 2 paren- tal alleles can be very different, a phenomenon known as allele-specific expression. Genomic imprinting is a prominent underlying mechanism in which the expres- sion of alleles is determined by their parental origin. The intensity ranges from unequal expression to the complete repression of 1 parental allele, equivalent to a functional haploidy. This leads to expression patterns noticeably deviant from the classic Mendelian inheri- tance models. In mammals, this mechanism is essential for embryogenesis, observable in the failure of parthe- nogenetic embryos to develop because of the funda- mental functional differences of the parental genomes (McGrath and Solter, 1984; Surani et al., 1984). Im- pairments of mechanisms related to genomic imprinting can result in serious developmental defects. Genomic imprinting is an epigenetic modification that changes the function of the involved DNA without altering the nucleotide sequence, primarily by DNA methylation (Reik et al., 1987; Sapienza et al., 1987; Swain et al., 1987). Although differentially methylated regions are found in almost every imprinted domain, other mech- anisms, such as histone and chromatin modification, might be of importance in the parent-of-origin ( par )- specific epigenetic marking of the DNA.
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2010-Boysen_et_al - Detection of a quantitative trait locus...

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