Diploid gynogenesis in Xenopus laevis and the localization with respect to the centromere of the gene for periodic albinism ap.

Diploid gynogenetic Xenopus laevis were obtained by inseminating the eggs with u.v. irradiated spermatozoa, and treating them with hydrostatic pressure to inhibit the expulsion of the second polar body. A u.v. dose of 3000 ergs/mm2 genetically inactivates the spermatozoa without loss of their ability to activate egg development. The use of a genetic marker on very large samples of eggs made it possible to verify the efficiency of the methods employed. The comparison of the development of diploid gynogenetic embryos with that of haploid gynogenetic, triploid and diploid controls makes it very probable that the relatively high mortality or abnormal development obtained with the pressurized eggs is not due to partial homozygosity but rather to physical damage to the egg structure by this treatment. Altogether about 2500 developing eggs were used. In addition diploid gynogenetic reproduction from females heterozygous for a known mutation allows the mapping of the gene concerned relative to the centromere on the basis of the recombination rate. For this experiment we used the recessive mutation causing periodic albinism (ap) and found the position of this gene to be between 44 map units from the centromere and the end of the chromosome.