<p> Evidence of gene conversion and inter=allelic complementation from earlier work on the pdx-1 locus of Neurospora crassa suggested that a more detailed analysis of this locus should lead to a better understanding of these genetic phenomenao The work described in this thesis is concerned with the derivation of complementation maps for seven alleles of the pdx-1 locus, and with a study of recombination between these alleles through the isolation of prototrophs from suitably marked inter-allelic crosses together with the isolation of asci including those exhibiting the phenomenon of gene conversione In additioni the relationships betwean the pdx-1 alleles and a gene, en-pdx-1, affecting the excretion of a pigment into the medium on which the pdx-1 strains were grown were studied. The effect of desoxypyridoxine hydrochloride 9 and the extent to which the pdx-1 mutants respond to various normal forms of the vitamin, were also studied. </p> / Thesis / Doctor of Philosophy (PhD)