MITOTIC RECOMBINATION IN STABLE AND UNSTABLE CHROMOSOME-III DISOMICS OF ASPERGILLUS-NIDULANS

Approximately 2% of the haploid breakdown sectors of heterozygous chromosome III disomics of Aspergillus nidulans are the result of recombination between the homologous chromosomes. The exchanges are concentrated between the two mutations spanning the centromere. Comparisons are made between disomics hemizygous for the sodIIIA1 mutation (Upshall et al. 1979) which are stable when grown at 37.degree. C, and disomics carrying the wild type allele of the sodIIIA1 locus, which are unstable under all conditions. It is shown that neither temperature nor the sodIIIA1 mutation affect the frequency or pattern of recombination between the homologues.