Three Structure-Selective Endonucleases Are Essential in the Absence of BLM Helicase in Drosophila
(A-B) DAPI-stained metaphase neuroblast nuclei. Normal wild-type nuclei (A) contain one pair of sex chromosomes, two pairs of large autosomes, and one pair of small autosomes. Most nuclei of single mutants for mus81, mus309, Gen, or mus312 are normal (see Figure 4). (B) An example of a cell from a mus312 mus309 mutant, illustrated polyploidy and broken chromosomes (arrowhead). (C-F) DAPI-stained larval salivary gland nuclei. Arrows point to polyploid nuclei; arrowheads point to diploid imaginal nuclei. Compared to wild-type (C) and mus309 (D) and mus312 (E) single mutants, diploid imaginal ring cell nuclei are reduced in number and enlarged in size in mus312 mus309 double mutants (F) and in Gen mus309 spn-A (not shown). Endocycling polytene cells are similar in all genotypes shown.