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Chance as a Cause of Changes in Gene Frequency Within Pure Breeds of Livestock

Jay L. Lush
The American Naturalist
Vol. 80, No. 792 (May - Jun., 1946), pp. 318-342
Stable URL: http://www.jstor.org/stable/2457852
Page Count: 25
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Chance as a Cause of Changes in Gene Frequency Within Pure Breeds of Livestock
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Abstract

Chance deviations in gene frequency from one generation to the next, as a result of Mendelian sampling and the elimination of potential parents, are important in the pure breeds of livestock. Standard deviations of the order of .02 to .05 for gene frequencies near .5 seem to be about the usual magnitude of these chance changes in one generation. The major cause for these changes being so much larger than would be required automatically by the finite size of the population seems to be inequality in the number of gametes which the various potential parents actually contribute to the next generation. Attention to family and pedigree, plus the economic incidents which happen to whole herds, probably emphasize this more in livestock than is usual in most species in nature, although this statement about pure-bred live-stock as compared with wild species is an expression of faith which might be severely shaken if we knew more about the actual pedigrees of wild organisms!

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