Step 2 From gene targeted Es cells to gene targeted mice 5. Injection of Es cells into blastocysts The targeted ES celis where they mix and form a mosaic The injected blastocysts are implanted are injected with the cells of the inner cell mass into a surrogate mother where they into blastocysts. from which the embryo develops, develop into mosaic embryos. Mosaic inner ell mass 6. Birth and breeding Born mosaic mice of mosaic mice The mosaic mice mate with normal mice to produce both gene targeted and nomal offspring Mosaic mouse d rmal mous ♀ 9 Gene targeted mice-called"knockout Normal mice mice when the targeted gene is inactivated c The Nobel Committee tor Physiolog or Medcine Hbstratom: Anka Rol