RESUMO
We have used a new approach involving in situ hybridisation and electron microscopy to establish ultrastructural homologies between polytene chromosome regions of Drosophila melanogaster and Drosophila subobscura. Twelve probes were chosen to cover all the chromosomal elements: the myospheroid gene, the collagen type IV gene, the collagen-like gene, the w26 homeobox gene, the beta3 tubulin gene, the kinesin heavy chain gene, the tryptophan hydrolase gene, the Hsp82, Hsp22-26 and Hsp23-28, Hsp68, Hsp70 genes and the beta unit of the F0-F1 ATPase gene. Most of these loci were previously undescribed in D. subobscura and imprecisely located in D. melanogaster. We have demonstrated here, by an ultrastructural analysis of each chromosomal region, that homologous genetic loci tend to show a similar ultrastructure in the two species. With a few exceptions, the structural homology extends to the chromosomal regions surrounding the loci. In some cases, however, no structurally recognisable homology can be seen either in the locus or in its flanking regions.
Assuntos
Cromossomos/ultraestrutura , Proteínas de Drosophila , Drosophila melanogaster/genética , Genes de Insetos , Proteínas Musculares , Homologia de Sequência do Ácido Nucleico , Animais , Bandeamento Cromossômico , Colágeno/genética , Sondas de DNA , Drosophila melanogaster/ultraestrutura , Proteínas de Choque Térmico HSP20 , Proteínas de Choque Térmico HSP30 , Proteínas de Choque Térmico HSP70/genética , Proteínas de Choque Térmico/genética , Cadeias alfa de Integrinas , Integrinas/genética , Cinesinas/genética , Proteínas de Membrana/genética , ATPases Translocadoras de Prótons/genética , Triptofano Hidroxilase/genética , Tubulina (Proteína)/genéticaRESUMO
Immunofluorescent techniques have been used in the analysis of DNA-RNA hybrids occurrence and its relationship to transcriptional events on polytene chromosomes of Drosophila subobscura. We have studied the distribution of these hybrids on uninduced/induced chromosomes. Two different indirect immunofluorescence methods for the detection of DNA-RNA hybrids were used. Our data confirm the positive correlation between localization of DNA-RNA hybrids and transcriptional activity by following the Büsen et al procedure (1982). Using the other protocol, which allows chromosomal DNA-RNA to denature and renature, makes DNA-RNA hybrids detectable not exclusively in active chromosomal regions. Taking Büsen as method of choice, this technique allowed to localize the exact transcriptional active sites on puffs: hybrid fluorescence was restricted to marginal or central puff areas. Moreover, no correlation between fluorescence and puffs size was found. However, our studies on induced chromosomes indicate that: 1) the 15DE puff, previously described as t-puff, was not really a heat shock puff, since no transcriptional activity was detected; 2) hybrid fluorescence at 2C and 31CD regions was observed. No labelling was found in these loci in the autoradiography data, reported by other authors.
Assuntos
DNA/análise , Drosophila/fisiologia , RNA/análise , Estresse Fisiológico/fisiopatologia , Transcrição Gênica , Animais , Cromossomos/química , Cromossomos/ultraestrutura , Drosophila/genética , Imunofluorescência , Regulação da Expressão Gênica , Desnaturação de Ácido Nucleico , Hibridização de Ácido Nucleico , RNA Mensageiro/biossíntese , Estresse Fisiológico/genéticaRESUMO
The ultrastructure of the Drosophila subobscura chromosome regions around the breakpoints of the complex E1 + 2 + 9 + 12 gene arrangement was analyzed. This overlapping inversion is formed by the association of the E1, E2, E9, and E12 simple inversions. Ultrastructure of sections involving 58D/59A, 61C/D, 62D/63A, 64B/C, 67A/B, and 68B/C breakpoints on Est chromosomes were compared with the ultrastructure of sections involving chromosomes were compared with the ultrastructure of sections involving 58D/68B, 62D/64C, 59A/63A, 64B/68C, 67B/61C, and 67A/61B breakpoints on E1 + 2 + 9 + 12 chromosomes. No detectable changes of structural organization on banding patterns induced by the E1 + 2 + 9 + 12 inversion were found. Ultrastructural analysis of the two E12 breakpoints has, however, facilitated the analysis of the left boundary of E12 inversion. Accordingly, we propose 61B/C as a new breakpoint instead of 61C/D.
Assuntos
Cromossomos/ultraestrutura , Drosophila/genética , Animais , Bandeamento Cromossômico , Drosophila/ultraestrutura , Microscopia EletrônicaRESUMO
The banding pattern of the divisions 57, 58 and 59 of the E polytene chromosome of Drosophila subobscura was analyzed by electron microscopy. Using squashed and thin-sectioned polytene chromosomes, our electron microscopic results have been compared with the reference map of Kunze-Müller (Chromosoma 9, 559-570 (1958]. These divisions are rich in heavy bands, and their number and location coincide with those of the reference map. The major differences observed between our electron micrographs and the reference map have been at the level of faint bands.
Assuntos
Cromossomos/ultraestrutura , Drosophila/genética , Animais , Bandeamento Cromossômico , Microscopia EletrônicaRESUMO
Revision of the reference map of the polytene chromosomes of Drosophila subobscura was started by means of the electron microscope. We present a map of regions 70B to 72D of the E chromosome obtained from squashed and thin-sectioned salivary glands. It was observed that the total number of bands in divisions 70B to 72D is considerably higher than those depicted in the reference map of Kunze-Mühl and Müller. Functional considerations are made of some regions that show puff structures.