Structural organization of the genome of the zygomycete Absidia glauca: evidence for high repetitive DNA content

Summary Total cell DNA of Absidia glauca has a GC-content of 44.6% ± 0.5% as determined from optical melting profiles which is in good accordance with values from equilibrium centrifugation in bisbenzimide containing CsCl gradients (46.2% = 1.1%), whereas mitochondrial DNA has a GC-content of only 30%. The genome size of Absidia glauca is approximately 36,000 kb, 8.6 times that of Escherichia coli. Three kinetically different fractions could be identified in reassociation experiments: a foldback-DNA fraction, comprising approximately 10% of the total DNA, repetitive DNA (25%) and single copy DNA (65%). This relatively high amount of repetitive DNA could partly be ascribed to ribosomal DNA (13%) and a new interspersed repetitive element (rAg1) which has been cloned in pBR325.