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Natal Influences and Twin Differences

Van den Daele, Leland D.
Publication Year:
Report Number:
ETS Research Bulletin
Document Type:
Page Count:
Subject/Key Words:
Genetics, Individual Characteristics, Infants, Prenatal Influences


A classification of natal influences is proposed with a model of their operation. Natal influences affect maternal capacity, maternal load, and maternal efficiency. Since maternal load is increased in twin pregnancy, results of twin studies must be generalized with caution. The method of co-twin control is exemplified by examination of a small sample. The results of the intrapair analysis imply that current formulations of hereditary and environmental contributions to phenotypic variation are inadequate to account for observed intrapair differences. Two alternative, though nonexclusive, interpretations of intrapair variation are suggested. The first interpretation stresses the role of complex maternal-fetal-environmental interactions, and the second, a "genetic indetermination" which derives, in part, from the information characteristics of the genes. (Author) (37pp.)

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