Fig. 4. Centrosome replication in bubR1^Rev1 embryos. In all panels, DNA is in red, centrosomes are in (A-C) green or (E-H) blue with tubulin in green. (A) Cortical section of a 3 hour AEL wild-type embryo showing a homogeneous distribution of nuclei, each associated with a pair of centrosomes. (B) bubR1^Rev1 embryo at 1 hour AEL showing well-separated centrosomes at the cortex and almost complete absence of nuclear DNA. (C) Cortical section of bubR1^Rev1 embryo at 3 hours AEL showing regions with no nuclei and areas with large number of centrosomes. (D) Quantification of the number of centrosomes per area in either wild-type (black squares) or mutant embryos (white circles) at different times AEL (minutes). Asterisk refers to embryos in A,C. (E-H) Mitotic spindles at nuclear cycles 10-11 in bubR1^Rev1 embryos. (E) Abnormal distribution of barrel-shaped spindles (arrow) showing centrosomes (arrowhead) abnormally close to a centrosome from an adjacent spindle. (F) Fused spindles without proper separation of centrosomes at the spindle poles (arrow); other spindles assemble normally but show lagging chromosomes during anaphase (arrowheads). (G) Monopolar spindles resulting from loss of centrosomes (arrowhead), spindles that share centrosomes (asterisk) and free centrosomes (arrow) are able to nucleate microtubules. (H) Excess centrosomes perturb spindle assembly and chromosomes segregation. Scale bars: 20 µm in A,C; 50 µm in B; 10 µm in E-H.