Partner Choice in Spontaneous Mitotic Recombination in Wild Type and Homologous Recombination Mutants of

, the most common fungal pathogen, is a diploid with a genome that is rich in repeats and has high levels of heterozygosity. To study the role of different recombination pathways on direct-repeat recombination, we replaced either allele of the gene (Chr6) with the -blaster cassette (), measured rates of loss as resistance to 5-fluoroorotic acid (5FOA) and used CHEF Southern hybridization and SNP-RFLP analysis to identify recombination mechanisms and their frequency in wildtype and recombination mutants. FOA rates varied little across different strain backgrounds. In contrast, the type and frequency of mechanisms underlying direct repeat recombination varied greatly. For example, wildtype, and strains all displayed a bias for loss via pop-out/deletion inter-homolog recombination and this bias was reduced in mutants. In addition, in -derived 5FOA strains direct repeat recombination was associated with ectopic translocation (5%), chromosome loss/truncation (14%) and inter-homolog recombination (6%). In the absence of , loss was mostly due to chromosome loss and truncation (80-90%), and the bias of retained allele frequency points to the presence of a recessive lethal allele on Chr6B. However, a few single-strand annealing (SSA)-like events were identified and these were independent of either Rad59 or Lig4. Finally, the specific sizes of Chr6 truncations suggest that the inserted URA-blaster could represent a fragile site.