Fig. 1. Cytological analysis and quantification of mitotic phenotypes in mast mutant neuroblasts. Third instar larval brains were dissected from wild-type (A and G) or mast mutant (B–F and H–K) individuals. Wild-type cells in metaphase (A) or anaphase (G) are shown for comparison. mast mutant cells show either diploid (B) or polyploid (C) circular mitotic figures (CMF) with chromosomes organized with their centromeres facing a central region where the small fourth chromosomes are located. Most cells show highly condensed chromosomes (B–F, J and K). mast mutant cells at anaphase (H and I) can also be found and occasionally show chromatin bridges and abnormal segregation. In the most severe mastP4 allele, cells show extensive polyploidy with most chromosomes organized in a sphere-like conformation (F). (L) Quantification of mitotic index. (M) Quantification of mitotic cells with respect to different stages of mitosis. (N) Quantification of the abnormal mitotic parameters in all alleles. Bar = 5 µm except in (J) and (K), 50 µm.