Electron microscopic studies of giant nucleus-like structure formed by lambda DNA introduced into the cytoplasm of...

When bacteriophage lambda DNA was injected into the cytoplasm of the fertilized egg of Xenopus laevis, giant nucleus-like structures were assembled around the injected DNA. These nucleus-like structures survived during cleavage and were partitioned into blastomeres at the blastula stage. The nucleus-like structures formed in the uncleaved fertilized eggs and the blastula cells were both surrounded by a bilayer nuclear membrane with nuclear pore complexes. The ultrastructural features of the lambda DNA-induced nucleus-like structure were considerably different from those of the normal blastula nucleus: although the nuclear pore complexes appeared to be normal, the 'nucleoplasm' was much too homogeneous as compared with that of the normal nucleus.