Organization and Transcription of DNA in Chromosomes and Mitochondria of Drosophila

Abstract

Although Drosophila chromosomes are fundamental to our understanding of cytogenetics, the organization of their DNA is a topic on which data and interpretations are of ten in conflict. However, some general aspects of the organization of Drosophila DNA and of polytene chromosomes can be inferred from the analysis of DNA renaturation. We first discuss recent experiments which indicate that (a) in contrast to the conclusions of Lee and Thomas (1973), renaturation kinetics can rule out a general model of tandem repetition of sequences; and (b) DNA in euchromatic arms of polytene chromosomes represents the distribution of euchromatic sequences in nonpolytene cells. Based on a specific model of sequence distribution discussed here, the data on ring formation with salivary gland DNA of D. hydei are reasonably consistent with renaturation kinetic data.