The Cytogenetic Analysis of a Fractured Gene in Drosophila

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RESUMO

The data presented in this study are derived from the analyses of Notch mutants known to be associated with visible cytological deficiencies. One mutant, Df(1)N62b1, described as a right-side deficiency, bears a deletion that apparently initiates within the Notch locus and extends to the right as far as the locus of dm. Recombination experiments using heterozygotes of Df(1)N62b1 with a series of intragenic point mutants within the Notch cistron suggest that this deficiency represents a deletion for the right-end portion of the gene. A consideration of the cytology of Df(1)N62b1 supports the cytogenetic inference that, if a Notch locus-3C7 relationship is valid, the missing portion of the gene as assayed by recombination experiments has an interband position between 3C7 and 8.—The data derived from two left-side deficiencies with a genetic lesion in Notch and a deletion extending to w are somewhat equivocal, but they do support the presumed Notch locus-3C7 band relationship and thereby enhance the likelihood that Df(1)N62b1 is correctly interpreted.—Cytogenetic information presently available suggests that, although a significant portion of the Notch cistron has a position on the salivary map identified as interband 3C7 to 8, the 3C7 band is part of the total picture of the Notch gene.

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