Strain-dependent variation in ribosomal DNA arrangement in Absidia glauca.

Restriction analysis of total DNA from the zygomycete Absidia glauca reveals a pattern of prominent bands on a homogeneous background. By Southern blot analysis with 32P-end-labelled ribosomal RNA most of these bands could unequivocally be identified as repetitive copies of ribosomal DNA. There are marked differences in restriction patterns of rDNA between all seven strains tested, even of strains belonging to mating type pairs, presumably isolated from the same location. By using purified rRNAs as probes in hybridization experiments, evidence is presented that 5S rRNA is part of the ribosomal repetitive unit. A more detailed analysis of one strain pair [A. glauca CBS 100.48 (+)/101.48 (-)] provided evidence that the (+) strain, in addition to one rDNA repeat unit common to both strains, contains a second one, derived from the common form by a small deletion.