Genetic Analysis of the Dento-Facial Growth and Development.

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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.