A genetic study on the length of tibia.

The length of tibia was studied in 1364 males and 1791 females over 10 years of age in an agricultural district of Wakayama Prefecture, Japan. (1) The length markedly increased from 10 to 17 years of age in males, and 10 to 15 in females, but it remained comparatively unchanged from 20 to 79 years in both sexes. The following regressions of tibial length covering 20 to 79 years were obtained: Y male = 0-0183x+34-7892, Y female = -0-0269x + 32-5329. The modified data proved to be a normal distribution on skewness and kurtosis test; they were analysed on a quantitative genetic basis. (2) No significant contribution of X-linked and Y-linked genes to tibial length was found in an analysis of parent-child combinations. (3) There was no indication of maternal effect, since the difference between father-child (r = 0-36 +/- 0-05) and mother-child (r = 0-42 +/- 0-04) correlations was not significant. (4) Correlation coefficients between sibs were significant, the values being 0-57 +/- 0-09 for brother-brother, 0-32 +/- 0-22 for sister-sister, and 0-27 +/- 0-13 for brother-sister. Correlation coeffiecients between parent and child were also significant, the values being 0-36 +/- 0-06 for father-son, 0-35 +/- 0-09 for father-daughter, 0-44 +/- 0-04 for mother-son, 0-35 +/- 0-07 for mother-daughter. The regression coefficients of child on midparent were calculated to be 0-77 +/- 0-12. Thus, the heritability for the length of tibia may be estimated to be 0-77 approximately 0-80. Contribution of dominance variance to total variance was very small (VD = 0-01), in contrast to a far greater additive genetic variance (VA = 0-80).