Abstract
Simple heritability estimators of continuous as well as discrete traits from twin data are known to overestimate the degree of genetic determination of the measured traits for several reasons. Errors of zygosity determination will, however, underestimate the true heritability. The bias due to wrong assignment of dizygous twin pairs into monozygous type is evaluated here, and the results indicate that this negative bias has a compensatory effect on the estimate of the degree of genetic determination when other factors of similarity between twin pairs are taken into account. It is shown that when an estimate of zygosity error is available, the bias due to this factor can be evaluated quantitatively, and hence the adjustment for zygosity error can be incorporated in the estimation of the degree of genetic determination of a trait.
Although this theory is explicitly developed here for twin studies, the general principle also applies for other types of errors of determining the degree of biological relationships for estimation of heritability, in which case this type of error may be more important than the simple zygosity error.
Similar content being viewed by others
References
Abramowitz M. &Stegun I.A. 1970.Handbook of Mathematical Functions. Dover Publications, New York.
Cavalli-Sforza L.L. &Bodmer W.F. 1971.The Genetics of Human Populations. Freeman, San Francisco.
Chakraborty R. 1979.Twin zygosity diagnosis by genetic systems — An efficiency evaluation. Acta Genet. Med. Gemellol., 28: 77–79.
Chakraborty R., Weiss K.M. &Ward R.H. 1980.Evaluation of relative risks from the correlation between relatives: A theoretical approach. Medical Anthropol., 4: 397–414.
Eaves D.S. 1965.The inheritance of liability to certain diseases, estimated from the incidence among relatives. Ann. Hum. Genet., 29: 51–76.Falconer D.S. 1981.Introduction to Quantitative Genetics. Second Edition. Longman, London.
Holzinger K.J. 1929.The relative effect of nature and nurture on twin differences. J. Edu. Psychol., 20: 241–248.
Jörensen G. 1974. Erbfaktoren bei hâufigen Krankheiten. In: Handbuch der Allgemeinen Pathlogie: Vol. IX. F. Vogel, ed. Erbgefüge, Springer, Heidelberg, pp. 581–665.
Lathrop G.M. 1980.Statistical methods in pedigree analysis and reliability of pedigree data. Ph. D. Dissertation, Univ. Washington, Seattle.
Neel J.V. &Schull W.J. 1954.Human Heredity. Univ. Chicago Press, Chicago.
Nichols R.C. &Bilbro W.C. 1966.The diagnosis of twin zygosity. Acta Genet., 16: 265–275.
Osborne R.H. &De George F.V. 1959.Genetic Basis of Morphological Variation. Harvard Univ. Press, Cambridge, MA.
Smith S.M. &Penrose L.S. 1955.Monozygotic and dizygotic twin diagnosis. Ann. Hum. Genet., 19: 273–289.
Snedecor G.W. &Cochran W.G. 1967.Statistical Methods. Sixth Edition. Iowa Univ. Press, Ames.
Stern C. 1973.Principles of Human Genetics. Third Edition. Freeman, San Francisco.
Vogel F. &Motulsky A.G. 1986.Human Genetics: Problems and Approaches. Springer-Verlag, Heidelberg — New York, Second Edition.
Von Verschuer O. 1958.Die Zwillingsforschung im Dienste der inneren Medizin. Verh. Dtsch. Ges. Inn. Med., 64: 262–273.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Chakraborty, R. Bias of heritability estimates from twin data in presence of errors of zygosity determination. Int. J. Anthropol. 5, 33–42 (1990). https://doi.org/10.1007/BF02442370
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF02442370