POLARITY OF MEIOTIC GENE CONVERSION IS 5' TO 3' WITHIN THE NIAD GENE OF ASPERGILLUS-NIDULANS

We have examined polarity of meiotic gene conversion in the niiA-niaD gene cluster of Aspergillus nidulans in two-point crosses. The type an d position of the mutations represented by the niaD alleles and the co rrelation between the relative frequency of gene conversion and the ph ysical position of these mutations were determined. We show that polar ity of meiotic gene conversion is 5' to 3' (transcribed strand) within the niaD gene. Additional crosses involving a niiA allele and a niaD allele show little polarity of gene conversion, which suggests that th e recombination events leading to restoration of the niaD gene are ini tiated upstream of the coding region of the niaD gene but within the n iiA-niaD gene cluster, possibly within the intergenic promoter region.