In situ study of chorion gene amplification in ovarian follicle cells of Drosophila nasuta

The temporal and spatial pattern of replication of chorion gene clusters in follicle cells during oogenesis in Drosophila melanogaster and Drosophila nasuta was examined by [ thymidine autoradiography and by in situ hybridization with chorion gene probes. When pulse labelled with [H] thymidine, the follicle cells from stage 10-12 ovarian follicles of both Drosophila melanogaster and, Drosophila nasuta often showed intense labelling at only one or two sites per nucleus. In situ hybridization of chorion gene probes derived from Drosophila melanogaster with follicle cell nuclei of Drosophila melanogaster and Drosophila nasuta revealed these discrete [H] thymidine labelled sites to correspond to the two amplifying chorion gene clusters. It appears, therefore, that in spite of evolutionary divergence, the organization and programme of selective amplification of chorion genes in ovarian follicle cells have remained generally similar in these two species. The endoreplicated and amplified copies of each chorion gene cluster remain closely associated but the two clusters occupy separate sites in follicle cell nucleus. © 1990 Indian Academy of Sciences.