Fig. 5. Strategy for analysis of Cripto in aggregation chimeras. (A) Morula aggregation is performed between wild-type unmarked embryos and Rosa26-marked embryos from a cross between Cripto heterozygous parents [adapted from Rivera-Perez et al. (Rivera-Perez et al., 1999)]. One-quarter of the chimeras will contain marked Cripto-null cells (Rosa26/+; Cripto^lacZ/del +/+), while the remaining three-quarters will be phenotypically wild type and serve as internal controls. (B) Extra-embryonic regions from ß-galactosidase-stained chimeric embryos genotyped by PCR; analysis of a representative litter is shown.