Molecular characterization of the horizontal gene transfer between mycoparasite parasitella parasitica and its host absidia glauca Parasitella parasitica is a zygomycetous mycoparasite with several hosts in Mucorales. During the infection process it transfers nuclei and other cellular components to its hosts through biotrophic fusion. Gene transfer was proven by the formation of para recombinants after infection with the genetic background of the host plus some additional traits from the parasite. In this thesis natural horizontal gene transfer system has been studied for the first time at the molecular level with respect to chromosomally located genetic markers. For this purpose a P. parasitica adenine auxotrophic mutant was employed as DNA donor whereas a methionine auxotroph A. glauca served as recipient. The resulting methionine prototrophic hybrids were selected and analyzed for their properties ...