POLYTENE CHROMOSOMES - A GENERAL-MODEL FOR THE EUKARYOTIC INTERPHASE STATE

The euchromatic structures of insect polytene chromosomes represent an amplified version of the chromomeric organization in diploid chromati n. As such, they are an excellent model system for studying structure/ function relationships of eucaryotic interphase chromosomes. Polyteniz ation is accomplished by replication patterns that are different for e uchromatic and heterochromatic chromatin and also seem to depend on th e functional state of chromatin. In Diptera, polytene chromosomes are characterized by genetically determined discontinuities of DNA packing in bands and interbands that are modified by functional demands. The cytological visualization of proteins that are associated with the com paction and decondensation of chromatin, allows the analysis of the te mporal and spatial dynamics of DNA/protein interactions in the context of structure, transcription, and the processing of RNA. Ribonucleopro tein particles may be followed on their way via the nuclear matrix thr ough the pores of the nuclear envelope to the cytoplasmic compartment. Thus, polytene nuclei provide unique opportunities for studying the f low of genetic information from the site of storage to the site of act ion, i.e. from gene to phenotype. Copyright (C) 1996 Elsevier Science Ltd.