Redundant DNA of Neurospora crassa

Approximately 20% of the DNA of Neurospora crassa consists of redundant sequences. This is calculated from the reassociation rate of fragmented, denatured DNA as measured by hydroxyapatite column chromatography. The redundant DNA has a complexity of 10⁵ base pairs and a repetition frequency of up to 60 copies per genome. Its buoyant density in CsCl is 1.720 g/ml and its hypochromicity 20–24%. Base composition determination shows 54% GC content like Neurospora nuclear DNA. DNA-RNA hybridization studies indicate that rRNA and tRNA cistrons make up 2.3 and 1.2%, respectively, of the redundant fraction. Pulse-labeled RNA is shown to hybridize with both redundant and unique DNA fractions, suggesting that both fractions are transcribed.This work is supported by a grant from National Science Foundation (GB 8058) and National Institute of Health Research Career Development Award (K3GM31-238).