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The combinations of the sexes in twin lambings

Published online by Cambridge University Press:  14 April 2009

William H. James
William H. James
Affiliation:
The Galton Laboratory, University College London, Wolfson House, 4 Stephenson Way, London NW1 2HE
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Summary

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Evidence is presented that the distribution of the combinations of the sexes in twin lambings has subnormal dispersion: there are more opposite-sexed pairs than same-sexed pairs. When adjustment is made for the occasional presence of monozygotic twin pairs, the departure from expectation (on the assumption that the sexes of DZ twins are distributed binomially) is highly significant. Thus sheep litters seem to show a feature characteristic of litters of pigs and (probably) mice and rabbits. This is consistent with the suggestion that p, the probability of a male zygote, varies systematically from one zygote to another within a litter.

Type
Research Article
Information
Genetics Research , Volume 28 , Issue 3 , December 1976 , pp. 277 - 280
Copyright
Copyright © Cambridge University Press 1976

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