Fig. 3. Homozygotes of the middle-copy number line M2 were embryonic lethal. (A) Lateral view of E10.5 nontransgenic, heterozygous and homozygous embryos. All heretozygous embryos were phenotypically indistinguishable from the nontransgenic littermates. All E10.5 homozygous embryos were markedly growth-retarded with severe cardiac defect. (B) Genotypic and phenotypic analysis of embryos from heterozygous matings, as described in the legend of Fig. 2.