Palate development in the mouse: a quantitative method that permits the estimation of time and rate of palate closure

A quantitative technique is used to express the morphogenetic stages of palate development in the mouse in terms of gestational age and the normal probability distribution. The qualitative palate rating scale for mouse embryos was modified and the numbers of embryos that had reached the different palate stages at specific gestational ages were fitted to a cumulative multinomial frequency distribution by normal probability regression on gestational age. The median time for each stage can be estimated and the standard deviation of this time (slope of the probability regression) provides a measure of the rate of development. A/J and A.B6 F1 embryos (A/J maternal environment) differed significantly in median time but not in rate of development during a restricted examination time.