MUTATION CHROMOSOME BOWS (CHB(V40)) ASSOC IATED WITH THE ABNORMAL CHROMOSOME SPINDLE IN DROSOPHILA-MELANOGASTER

Highly polyploid cells were detected in ganglia of Drosophila melanoga ster larvae homozygous for the chb(v40) mutation (78D) resulting from insertion of the P[IArB] construction. Frequency distribution of metap hases differing in chromosome number showed that the primary defect ca used by the mutation involved formation of the unipolar chromosome spi ndle. This was confirmed directly by cytological analysis. Circular mi totic figures (CMF), i.e., circles of chromosomes with centromeres poi nting inward and chromatid arms pointing outward, were also observed i n neuroblasts of the homozygotes. Such structures are characteristic o f polo and mgr mutations that alter the functions of the centrosome.