ABSTRACT
Genetic analysis of the asexual fungus Aspergillus niger is based on genetic recombination in somatic cells and requires proper genetic markers. Transformation in Aspergillus results from integration of the transforming DNA sequences in the genome of the recipient. Recombination of homologous transforming DNA may be at the homologous site either by single crossing over, by double crossing over, or by gene conversion. In special cases it may be useful to start transformation with a diploid strain constructed from two haploid strains together carrying markers for each chromosome. In this way time-consuming isolation of heterozygous diploids from each individual transform ant strain with a tester is avoided. Vectors with a heterologous marker may integrate at different sites in the genome, and multicopy transformants usually carry the plasmids as a single insert. An insert with a heterologous marker can be used as marker in genetic mapping and for the localization of genes lacking a detectable phenotype.
