CLONING OF VERTEBRATES - ADVANCES AND PRO BLEMS

Cloning of vertebrates, in particular, amphibians and mammals, is disc ussed. In the last decade, significant progress was made cloning mamma ls, while cloning of adult amphibians remained problematical. Low-trau matic methods of enucleation of recipient oocytes and transplantation of donor nuclei were worked out. In 1997, an adult sheep was cloned in Great Britain, thus demonstrating the possibility of cloning adult ma mmals. However, methods of cloning mammals need improvement because of the high lethality of reconstructed embryos (nuclear transplants). Th e use of in vitro cultured low-differentiated stem cells to obtain don or nuclei seems promising. Works on human cloning are not expedient in the near future because of technical and ethical aspects.