Genetic recombination in the nuclear, organellar, and plasmid genomes of eukaryotic organisms occurs during mitosis and meiosis. Mitotic recombination is an important mechanism for the repair of DNA damaged by ultraviolet light, ionizing radiation, and chemical agents (Friedberg et al. 1991). Moreover, nuclear chromosomal mitotic recombination is involved in a number of basic cellular processes seen in a wide variety of eukaryotic systems including: cell-type differentiation of homothallic budding yeast (Saccharomyces cerevisiae) (Strathern et al. 1982) and fission yeast (Schizosaccharomyces pombe) (Egel et al. 1984); transpositions of P-elements in Drosophila melanogaster (Gloor et al. 1991); mammalian and human site-specific V-D-J gene rearrangements that give rise to immunoglobulin and T-cell receptor diversity (Oettinger et al. 1990; Kallenbach and Rougeon 1992); and loss of heterozygosity implicated in carcinogenesis (Solomon et al. 1991). Meiotic recombination plays a key role in ensuring accurate chromosome segregation at the first meiotic division (the reductional division). Additionally, meiotic interchromosomal and intrachromosomal recombination of homologous DNA sequences between members of multigene families, such as the mammalian major histocompatibility complex, MHC, (Kuhner et al. 1991) and the isoaccepting multiple tRNA genes of fission yeast (Amstutz et al. 1985), contributes to allelic diversity and concerted evolution of members of multigene families. These recombinational events and conventional allelic meiotic gene conversion, crossing over, and independent assortment, produce an abundance of gametic genotypes.