(A) Haploid, (B) diploid and (C) triploid individuals can be generated following the transplantation of a random number of male nuclei during the REMI procedure. If the egg does not receive a nucleus, the embryo will be haploid and will not develop beyond the neurula stage (☹), unlike diploid and triploid animals that will give rise to founders (☺). (B) If the egg received a single nucleus, then the embryo generated will produce an heterozygous diploid F0 founder and lines can be derived as shown. Transgenic embryos can be selected by observing the expression of a marker gene, such as GFP, and individuals carrying the transgene (+) are isolated from non-carriers (−). (C) In the case of multiple nuclei transplantation, the embryos generated will be polyploid. It is not known how many nuclei can be maintained in Xenopus. Multiploid cells have been shown to suffer from chromosomal instability and degenerate. However, triploid individuals that result from transplantation of two male nuclei are stable and develop to adulthood (; ; ; ; ). It is not known if these animals are fertile (?) and whether lines can be derived form them. However, triploid embryos could be generated by REMI and maintained in animal facilities. (D) Finally, F0 diploid transgenic female founders can be made homozygous at the F1 generation by using a gynogenesis procedure. In this case, the genomic contribution of the male DNA is eliminated by UV treatment. The UV-treated spermatozoids are used for in vitro fertilization of the transgenic eggs. Inhibition of the first cleavage by pressure re-establishes the diploid state and development can proceed normally.