Developmental potential of somatic nuclei transplanted into meiotic oocytes of Rana pipiens.

Somatic nuclei, when transplanted into oocytes at the stage of first meiotic metaphase, were induced to undergo chromosome condensation and alignment on spindles. When the oocytes completed maturity in vitro and were activated, the somatic nuclei transformed into "fertilization" nuclei and promoted development through embryogenesis. Thus somatic nuclei can reversibly respond to cytoplasms directing either meiotic or mitotic events, and somatic nuclei from differentiated cells may be reversed by conditioning in oocytes.