Fig. 1. incenp^P(EP)2340 individuals show defects in chromosome segregation and cytokinesis. (A) Diagram of the Incenp genomic region showing insertion site of the P-element into the third exon of the Incenp gene in incenp^P(EP)2340. Black lines on either side of the P-element represent the genomic DNA fragments cloned by plasmid rescue and sequenced. Red boxes indicate the position of primers used for the PCR characterization of imprecise excision lines. Diagram of the Incenp transcript below shows the position of the point mutation (C to T) in incenp^EC3747. Below, diagrams of the predicted products of both Incenp mutants. (B) Northern blot, showing total RNA from wild-type and both Incenp mutants. Arrow points to truncated transcript present in heterozygous incenp^P(EP)2340/+ individuals. (C) Western blot analysis of wild-type embryos (WT), mutant embryos carrying a deficiency for the Incenp gene (DF), incenp³⁷⁴⁷ homozygous embryos (3747) and incenp^P(EP)2340 homozygous embryos [3747, [P(EP)]. Arrow points to wild-type Incenp protein. Lower panel shows -tubulin loading control. (D) Phenotype of incenp^P(EP)2340/+ in male meiosis. (Left) Wild-type onion-stage cyst; arrow points to individual spermatid with equal-size nucleus and mitochondrial derivative (Nebenkern). (Right) Same stage in incenp^P(EP)2340/+ males; notice large Nebenkerns indicative of defective cytokinesis (arrowhead), as well as variable-size nuclei indicative of problems in chromosome segregation (arrow).