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Comparative genetic variance and heritability of head and facial traits in northwest Indian and Belgian twins
Author(s) -
Sharma Krishan,
Susanne Charles
Publication year - 1991
Publication title -
american journal of human biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.559
H-Index - 81
eISSN - 1520-6300
pISSN - 1042-0533
DOI - 10.1002/ajhb.1310030402
Subject(s) - heritability , demography , biology , analysis of variance , population , statistics , genetics , mathematics , sociology
Genetic variance analysis of 13 head and facial traits is considered in samples of Northwest, Indian and Belgian twins. Modified t tests, based on the nested structure of twin data, indicate differences between monozygotic (MZ) and dizygotic (DZ) mean values of bigonial diameter in Indian females and in Belgian males, i.e., for only two of 52 instances. Heterogeneity of variance is observed in about 30% of the craniofacial traits in both samples, invalidating conventional within‐pair genetic variance estimates for these traits. Patterns of environmental bias on zygosities differ between sexes within the same population and also between the two samples. Revised average genetic variance ratios are higher in Indian than in Belgian twins. Male twins manifest, on average, higher genetic variance ratios than female twins in both the samples. There is stronger evidence of enviornmental covariance in MZ than in DZ twins for both Indian and Belgian twins. The pattern of intraclass corrlations, based on average values, is as follows: ♂r MZ > ♀r MZ > ♂r DZ ≥ ♀r DZ in the Indian twins and ♂r MZ > ♀r MZ > ♀r DZ > ♂r DZ in the Belgian twins.