Directional and anteroposterior asymmetry of common white markings in the legs of the Arabian horse: response to selection |
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Authors: | Charles M Woolf |
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Institution: | (1) Department of Zoology, Arizona State University, Tempe, AZ 85287-1501, USA |
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Abstract: | Arabian bay horses manifest, on the average, more common white markings in their hind legs than their forelegs (anteroposterior
asymmetry) and more common white markings in their left legs than their right legs (directional asymmetry). To determine if
genetic variation exists for these types of asymmetry, the phenotypic response was studied in bay foals when their dams and
sires were selected for the directions of fore-hind and left-right differences. In the fore-hind studies, the quantitative
shifts in the bay foals were in the direction specified by the selection scheme and the observed deviations were all statistically
significant. The shifts were also consistently in the direction favored by selection in the left-right studies, but only two
of six observed deviations were statistically significant using a one-tailed test of significance. Thus, only marginal statistical
evidence is available to support the observed consistent responses to selection in the left-right studies. These differential
responses are reflected in the magnitudes of the heritability estimates. Based on the overall results, it is concluded that
both types of asymmetry have a genetic basis in the Arabian horse, but much more genetic variation is present for anteroposterior
asymmetry than for directional asymmetry.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Arabian horse common white markings directional asymmetry anteroposterior asymmetry |
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