| Type | MGI:General | Description | homozygous null ES cells injected into wild-type blastocysts are capable of forming mesoderm in chimeric embryos; however, primitive streak formation is impaired wild-type ES cells injected into homozygous null blastocysts form relatively normal extraembryonic tissues and extraembryonic mesoderm; however, the embryo proper develops poorly, suggesting a severe gastrulation defect |
