A method for efficiently producing homozygous organisms from a heterozygous non-human starting organism, comprising providing of a heterozygous starting organism; allowing the starting organism to produce haploid cells; creating homozygous organisms from the haploid cells thus obtained; and selecting the organisms having the desired set of chromosomes, wherein during production of the haploid cells no recombination occurs in order to obtain a limited number of genetically different haploid cells. Recombination can also be prevented or suppressed.