关键词: 童年中期, 双生子, 下肢长, 遗传度

Abstract: Objective To assess the genetic and environmental influences on lower extremity length index of middle childhood twins,and the effect of the age and sex. Method The quantitative genetic model-fitting and estimates of each index and genetic and environmental variance components were done with Mx software. Results The best fitting model of each index was ACES.After adjusting age,the heritabilities was as follows:height (male 43%,female 60%),sitting height (male 62%,female 62%),lower extremity length (male 50%,female 62%) and lower extremity length ratio (male 18%,female 36%).There were gender differences in heritabilities of height,lower extremity length and lower extremity length ratio. Conclusion Environmental factors play a leading role in the development of body length,which suggests that nutrition,physical exercises and controlling related diseases should be paid much attention to improve lower extremity length development to promote children's growth potential.

Key words: middle childhood, twins, lower extremity length, heritability