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Race, Zygosity, and Mortality Among Twins: Interaction of Myth and Method

Published online by Cambridge University Press:  01 August 2014

C.E. Boklage
C.E. Boklage*
Affiliation:
Genetics Program, East Carolina University School of Medicine Greenville, North Carolina, USA
*
Genetics Program, East Carolina University School of Medicine Greenville, NC 27858-4534, USA

Abstract

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For epidemiological purposes, it is customary to assume that same-sex (SS) dizygotic (DZ) twin pairs are approximately equal in number to unlike-sex (OS)-DZs, the remainder of the SS pairs being monozygotic (MZ). It is also customary to consider OS-DZs to be epidemiologically representative of all DZs, which can only mean that difference in frequency of any trait between OS and SS twins is due to the MZ fraction of the SS twins. Since this is assumed as a premise, there is little value in its usual appearance as the result. The basic tenet of twin biology, that most twin excess anomalies are due to MZs, is a myth self-perpetuated by a methodological tautology, and is false, at least for mortality. In a consecutively ascertained and prospectively studied sample of 616 twin pairs, over 80% diagnosed for zygosity, it can be shown that the standard assumption mentioned above have given impossible answers. The most probable possible answer is that mortality does not differ greatly with zygosity overall, but that SSDZ mortality is much higher than that of OS twins, and probably even higher than that of MZs. Race differences in the probable answers further suggest that standard assumptions of the Weinberg method may have consistently provided false explanations for race differences in the OS fraction of twin pairs.

Keywords

Twin mortalityWeinberg methodZygosity
Type
Research Article
Information
Acta geneticae medicae et gemellologiae: twin research , Volume 36 , Issue 3 , July 1987 , pp. 275 - 288
Copyright
Copyright © The International Society for Twin Studies 1987

References

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