Potter R H, Nance W E
Am J Phys Anthropol. 1976 May;44(3):391-5. doi: 10.1002/ajpa.1330440303.
Bilateral tooth measurements in twins are partitioned into three orthogonal contrasts, each associated with one degree of freedom, to estimate three parameters: discordance, asymmetry, and mirror imagery. The probability levels of the within-pair variance ratios were used to test for significance of these estimates. The results provided strong evidences for the existence of significant genetic determinants of almost all of the individual tooth dimensions, but little or no evidence for a genetic basis of asymmetry. The analysis gave no indication that monozygotic twinning was associated with an increased degree of either fluctuating asymmetry or mirror imagery, when compared to dizygotic twins. The data on monozygotic twins further suggested that for most variables examined, the increment of environmental discordance resulting from the twinning phenomena was greater than the developmental noise that caused asymmetry within individual cotwins.
双胞胎双侧牙齿测量值被划分为三个正交对比，每个对比与一个自由度相关联，以估计三个参数：不一致性、不对称性和镜像对称性。通过对双胞胎内部方差比的概率水平进行检验，以确定这些估计值的显著性。结果提供了有力证据，表明几乎所有个体牙齿尺寸都存在显著的遗传决定因素，但几乎没有证据表明不对称性存在遗传基础。分析结果表明，与异卵双胞胎相比，同卵双胞胎并没有表现出更高程度的波动不对称性或镜像对称性。同卵双胞胎的数据进一步表明，对于大多数所研究的变量，双胞胎现象导致的环境不一致性增加幅度大于个体双胞胎内部导致不对称性的发育噪声。
