Genetic Analysis of the Dento-Facial Growth and Development.

连续变量，如牙齿大小和下颌大小，是可以根据连续尺度测量的特征。这种连续变量通常具有多因子基础；也就是说，几个基因和环境的影响，每一个都有相对较小的影响，有助于个体在连续尺度上的位置。多基因遗传，也称为多基因遗传或数量遗传，不容易分析，但已经开发了一些方法来证明它。其中最简单的方法是亲属之间的相似性方法；也就是说，两个个体的亲缘关系越近，他们在所讨论的特征上就越相似。通过实验动物的遗传研究表明，在颅面复合体的各个部分，遗传因子和母系因子之间存在着拮抗的“行为”。母性效应在雌性身上比雄性更早消失，这似乎与雌性比雄性更早达到成年体型有关。在牙面发育的早期，变异的主要来源是母体效应的变异，随着母体效应的减弱或消失，遗传效应成为决定牙面大小的一个更重要的因素。

The continuous variables, such as tooth size and jaw size, are characters that can be measured against a continuous scale. Such continuous variables usually have a multifactorial basis ; that is, several genes and environmental influences, each with a relatively small effect, contribute to an individual position on the continuous scale.Multivactorial inheritance, also known as polygenis or quantitative inheritance, is not easy to analyze, but a number of method have been developed to demonstrate it. The simplest of these is the method of resemblance between relatives ; that is, the demonstration that the more closely related two individuals are, the more closely they resemble each other in the trait in question.Based on the genetic study using the experimental animals it was indicated that there is the antagonistic "behavior" between the genetic and maternal factor through all experimental periods for each segment of the craniofacial complex. The maternal effect disappears earlier in females than males, and appears related to the fact that females attain adult size earlier than males. In the early stages of dento-facial growth, the main source of the variation is attributed to variance on the maternal effect, and later as the maternal effect decreases or disappears, the genetic effect becomes a more significant factor in determining the dento-facial size.