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The Monozygotic Twinning Rate: Is It Really Constant?

Published online by Cambridge University Press:  01 August 2014

G. Allen*
Affiliation:
U.S. Public Health Service, Retired, Bethesda, Maryland
Z. Hrubec
Affiliation:
National Cancer Institute, U.S. Public Health Service, Bethesda, Maryland
*
9326 W. Parkhill Dr., Bethesda, MD 20814, USA

Abstract

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Weinberg's difference method, applied to twin birth statistics, usually shows a dependence of the MZ rate on maternal age, like a thin shadow of the DZ rate. Some of this MZ variation could be explained away by James' finding of more same-sex (SS) than opposite-sex (OS) DZ twins, the excess being mistakenly classified as MZ by Weinberg's assumption of equal numbers. By several methods one can extract a Constant value for the MZ rate and a Constant or nearly Constant value for the DZ SS/OS ratio, but these “constants” are actually arbitrary and they vary between populations.

Type
Research Article
Copyright
Copyright © The International Society for Twin Studies 1987

References

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