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Title:   Author  item
                                            BOETTCHER, P - UNIVERSITY OF GUELPHitem
                                            JAIRATH, L - UNIVERSITY OF GUELPHitem
                                            Vanraden, Paul
  Submitted to: Journal of Dairy Science
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 9/6/2000
                                    Publication  Date: N/A
                                    Citation: N/AInterpretive Summary: This study tested for difference between genetic merits of sons and daughters of sires and for evidence of segregating quantitative trait loci on the X chromosomes of North American Holsteins. Son PTA adjusted for sire PTA was used as the dependent variable to test for biases and for genes that were passed from sire to daughter but not to son.  The test of  variability across sires of sons merely indicated an unaccounted source of variation, for which genes on X chromosomes might be responsible. Critical values for this test and power were determined by simulation for a variety of populations and traits differing in heritability, size of the X chromosome effect, and allelic frequency. Simulated genes on the X chromosome were detected with high power at intermediate frequencies of the favorable allele.  The power of the test increased as the size of the effect increased and as genetic variance attributed to autosomes  decreased.  The test was then applied to recently evaluated data for the US and Canadian Holstein populations. Genetic evaluations for >17,000 bulls from the US and >9000 from Canada were included.  Results suggested that a small amount of extra variation was present for some traits formally evaluated in North America, but that genes on the X chromosome were unlikely to be the cause.
                                Technical Abstract: This study tested for difference between genetic merits of sons and daughters of sires and for evidence of segregating quantitative trait loci on the X chromosomes of North American Holsteins. Son PTA adjusted for sire PTA was used as the dependent variable to test for biases and for genes that were passed from sire to daughter but not to son.  The test of  variability across sires of sons merely indicated an unaccounted source of variation, for which genes on X chromosomes might be responsible. Critical values for this test and power were determined by simulation for a variety of populations and traits differing in heritability, size of the X chromosome effect, and allelic frequency. Simulated genes on the X chromosome were detected with high power at intermediate frequencies of the favorable allele.  The power of the test increased as the size of the effect increased and as genetic variance attributed to autosomes  decreased.  The test was then applied to recently evaluated data for the US and Canadian Holstein populations. Genetic evaluations for >17,000 bulls from the US and >9000 from Canada were included.  Results suggested that a small amount of extra variation was present for some traits formally evaluated in North America, but that genes on the X chromosome were unlikely to be the cause.


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