Lung phenotype of double heterozygotes. a. Sections through the lungs of newborn wild-type (+/+ +/+), heterozygote for Smad2 (+/+ Smad2/+), heterozygote for Jeff (Jf/+ +/+) and two double heterozygote (Smad2/+ Jf/+) mice: with and without cleft palate. The sections were haematoxylin-eosin stained. Scale bars 200 μm. b. Graphic comparison of the number of airways for three regions of 5.3 × 106 μm2 taken at random and the width of airways for each genotype. P-values were determined using two-tailed T-test comparing each with the wild type.