Genetic study of the craniofacial growth in male rats by factor scores

The craniofacial growth of F₁ male offspring produced by a complete diallel cross of five strains of rats was observed with the use of cephalometry. Factor analysis was applied to several dimensions of dorsoventral and lateral cephalograms to assess the integration of the craniofacial complex with growth. The first three factors were chosen in each cephalogram, resulting in an explanation of 50.7% and 59.3% of the variation in the dorsoventral and lateral cephalograms, respectively, on an average throughout the period of the experiment, and disclosing that Factor I was associated most closely with the change in the craniofacial growth of rats. A further genetic analysis of the factor scores of each offspring lead to the conclusion that the growth changes of craniofacial width and length were more strongly influenced by the genetic effects; while those of upper jaw, nasal cavity, and pharyngeal part were more strongly influenced by the environmental effects.