Topologically significant dermatoglyphic patterns in twins.

A total of 58 dermatoglyphic characters, consisting of topologically significant pattern elements, i.e., loops and triradii, on palms, soles and fingertips, were tested in a sample of 110 MZ and 111 like-sexed DZ twin pairs. The analysis included homolateral, heterolateral and bilateral concordance rates, the derived Hc coefficient, coefficients of the within-pair association, phi, derived chi2 intraclass correlation coefficients and heritability estimates based on variances (h2) and correlations (Hr), and the variance ratio F. A considerable difference was found in respect of "heritability" values between palmar and sole patterns, in that they are the highest for sole loops and triradii and the lowest for most palmar loops. These data are compared with the h2 values obtained from family correlations. The difficulties in the interpretation of "heritability" estimates based on the material of twins are pointed out and particular attention is drawn to a possibility of the additional bias in twin studies related to a degree of symmetry of the characters investigated.