The fine genetic structure of the pabal region of Aspergillus nidulans

Abstract

The linear relationship between fourteen allelic p-aminobenzoic-acid-requiring mutants of Aspergillus nidulans was investigated. The mutants were assigned to twelve different mutational sites within one functional region. No case of intra-cistron complementation was found. The order of sites as determined by the distribution of the outside markers in different crosses between paba alleles is consistent and the recombination fractions between the sites are approximately additive. Crossing-over between alleles is associated with strong localized negative interference. The topography of the pabal region is characterized by a marked concentration of the mutational sites in a small part of the cistron.